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	$178.43	6.680%	$190.3491	$190.35	$190.35	$190.30
Purchase #2	$220.52	9.155%	$240.7086	$240.71	$240.70	$240.70
Purchase #3	$123.71	8.127%	$133.7639	$133.76	$133.75	$133.80
Purchase #4	$22.89	10.781%	$25.3578	$25.36	$25.35	$25.40
Purchase #5	$101.68	9.255%	$111.0905	$111.09	$111.10	$111.10
Purchase #6	$114.65	4.668%	$120.0019	$120.00	$120.00	$120.00
Purchase #7	$223.79	7.418%	$240.3907	$240.39	$240.40	$240.40
7 purchase totals =	$985.67		$1,061.6625	$1,061.66	$1,061.65	$1,061.70