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	$142.85	11.344%	$159.0549	$159.05	$159.05	$159.10
Purchase #2	$85.78	5.795%	$90.751	$90.75	$90.75	$90.80
Purchase #3	$41.34	7.427%	$44.4103	$44.41	$44.40	$44.40
Purchase #4	$193.34	9.655%	$212.007	$212.01	$212.00	$212.00
Purchase #5	$67.68	6.217%	$71.8877	$71.89	$71.90	$71.90
Purchase #6	$156.61	10.696%	$173.361	$173.36	$173.35	$173.40
Purchase #7	$131.56	7.525%	$141.4599	$141.46	$141.45	$141.50
7 purchase totals =	$819.16		$892.9318	$892.93	$892.90	$893.10