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	$180.77	8.703%	$196.5024	$196.50	$196.50	$196.50
Purchase #2	$243.69	6.502%	$259.5347	$259.53	$259.55	$259.50
Purchase #3	$187.98	3.852%	$195.221	$195.22	$195.20	$195.20
Purchase #4	$222.77	10.868%	$246.9806	$246.98	$247.00	$247.00
Purchase #5	$209.79	3.236%	$216.5788	$216.58	$216.60	$216.60
Purchase #6	$53.55	11.139%	$59.5149	$59.51	$59.50	$59.50
Purchase #7	$249.71	9.240%	$272.7832	$272.78	$272.80	$272.80
7 purchase totals =	$1,348.26		$1,447.1156	$1,447.10	$1,447.15	$1,447.10