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	$187.77	4.657%	$196.5144	$196.51	$196.50	$196.50
Purchase #2	$218.48	5.398%	$230.2736	$230.27	$230.25	$230.30
Purchase #3	$207.58	5.361%	$218.7084	$218.71	$218.70	$218.70
Purchase #4	$226.44	12.704%	$255.2069	$255.21	$255.20	$255.20
Purchase #5	$109.35	10.559%	$120.8963	$120.90	$120.90	$120.90
Purchase #6	$52.67	12.639%	$59.327	$59.33	$59.35	$59.30
Purchase #7	$38.77	4.842%	$40.6472	$40.65	$40.65	$40.60
7 purchase totals =	$1,041.06		$1,121.5738	$1,121.58	$1,121.55	$1,121.50