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	$149.76	12.771%	$168.8858	$168.89	$168.90	$168.90
Purchase #2	$130.51	8.721%	$141.8918	$141.89	$141.90	$141.90
Purchase #3	$164.86	6.844%	$176.143	$176.14	$176.15	$176.10
Purchase #4	$139.95	6.775%	$149.4316	$149.43	$149.45	$149.40
Purchase #5	$223.30	11.469%	$248.9103	$248.91	$248.90	$248.90
Purchase #6	$109.31	6.238%	$116.1288	$116.13	$116.15	$116.10
Purchase #7	$43.71	12.246%	$49.0627	$49.06	$49.05	$49.10
7 purchase totals =	$961.40		$1,050.4540	$1,050.45	$1,050.50	$1,050.40