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	$120.38	5.790%	$127.35	$127.35	$127.35	$127.40
Purchase #2	$231.31	10.784%	$256.2545	$256.25	$256.25	$256.30
Purchase #3	$196.37	9.458%	$214.9427	$214.94	$214.95	$214.90
Purchase #4	$167.55	7.283%	$179.7527	$179.75	$179.75	$179.80
Purchase #5	$152.98	6.267%	$162.5673	$162.57	$162.55	$162.60
Purchase #6	$194.67	11.343%	$216.7514	$216.75	$216.75	$216.80
Purchase #7	$133.49	9.256%	$145.8458	$145.85	$145.85	$145.80
7 purchase totals =	$1,196.75		$1,303.4644	$1,303.46	$1,303.45	$1,303.60