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	$90.37	12.552%	$101.7132	$101.71	$101.70	$101.70
Purchase #2	$245.50	13.804%	$279.3888	$279.39	$279.40	$279.40
Purchase #3	$49.40	3.392%	$51.0756	$51.08	$51.10	$51.10
Purchase #4	$55.47	10.220%	$61.139	$61.14	$61.15	$61.10
Purchase #5	$30.80	6.361%	$32.7592	$32.76	$32.75	$32.80
Purchase #6	$203.64	9.488%	$222.9614	$222.96	$222.95	$223.00
Purchase #7	$58.47	5.212%	$61.5175	$61.52	$61.50	$61.50
7 purchase totals =	$733.65		$810.5547	$810.56	$810.55	$810.60