Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$178.31	7.687%	$192.0167	$192.02	$192.00	$192.00
Purchase #2	$157.82	11.716%	$176.3102	$176.31	$176.30	$176.30
Purchase #3	$128.36	7.427%	$137.8933	$137.89	$137.90	$137.90
Purchase #4	$173.26	10.401%	$191.2808	$191.28	$191.30	$191.30
Purchase #5	$176.64	7.676%	$190.1989	$190.20	$190.20	$190.20
Purchase #6	$120.53	9.128%	$131.532	$131.53	$131.55	$131.50
Purchase #7	$147.81	12.272%	$165.9492	$165.95	$165.95	$165.90
7 purchase totals =	$1,082.73		$1,185.1811	$1,185.18	$1,185.20	$1,185.10