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	$224.98	3.616%	$233.1153	$233.12	$233.10	$233.10
Purchase #2	$227.81	6.542%	$242.7133	$242.71	$242.70	$242.70
Purchase #3	$72.46	9.487%	$79.3343	$79.33	$79.35	$79.30
Purchase #4	$53.25	11.403%	$59.3221	$59.32	$59.30	$59.30
Purchase #5	$163.25	4.276%	$170.2306	$170.23	$170.25	$170.20
Purchase #6	$83.30	11.357%	$92.7604	$92.76	$92.75	$92.80
Purchase #7	$177.47	3.770%	$184.1606	$184.16	$184.15	$184.20
7 purchase totals =	$1,002.52		$1,061.6366	$1,061.63	$1,061.60	$1,061.60