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	$159.92	3.629%	$165.7235	$165.72	$165.70	$165.70
Purchase #2	$203.29	6.106%	$215.7029	$215.70	$215.70	$215.70
Purchase #3	$207.47	5.232%	$218.3248	$218.32	$218.30	$218.30
Purchase #4	$202.41	6.762%	$216.097	$216.10	$216.10	$216.10
Purchase #5	$205.71	11.464%	$229.2926	$229.29	$229.30	$229.30
Purchase #6	$54.98	8.159%	$59.4658	$59.47	$59.45	$59.50
Purchase #7	$249.69	7.689%	$268.8887	$268.89	$268.90	$268.90
7 purchase totals =	$1,283.47		$1,373.4953	$1,373.49	$1,373.45	$1,373.50