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	$141.74	13.502%	$160.8777	$160.88	$160.90	$160.90
Purchase #2	$71.47	10.283%	$78.8193	$78.82	$78.80	$78.80
Purchase #3	$124.27	6.728%	$132.6309	$132.63	$132.65	$132.60
Purchase #4	$183.73	6.307%	$195.3179	$195.32	$195.30	$195.30
Purchase #5	$151.72	7.374%	$162.9078	$162.91	$162.90	$162.90
Purchase #6	$55.85	5.803%	$59.091	$59.09	$59.10	$59.10
Purchase #7	$239.95	5.314%	$252.7009	$252.70	$252.70	$252.70
7 purchase totals =	$968.73		$1,042.3455	$1,042.35	$1,042.35	$1,042.30