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	$218.85	6.521%	$233.1212	$233.12	$233.10	$233.10
Purchase #2	$54.37	10.227%	$59.9304	$59.93	$59.95	$59.90
Purchase #3	$46.78	13.106%	$52.911	$52.91	$52.90	$52.90
Purchase #4	$228.79	5.864%	$242.2062	$242.21	$242.20	$242.20
Purchase #5	$65.32	4.539%	$68.2849	$68.28	$68.30	$68.30
Purchase #6	$198.92	8.567%	$215.9615	$215.96	$215.95	$216.00
Purchase #7	$232.53	13.566%	$264.075	$264.08	$264.10	$264.10
7 purchase totals =	$1,045.56		$1,136.4902	$1,136.49	$1,136.50	$1,136.50