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	$52.69	12.810%	$59.4396	$59.44	$59.45	$59.40
Purchase #2	$77.74	10.165%	$85.6423	$85.64	$85.65	$85.60
Purchase #3	$209.46	10.261%	$230.9527	$230.95	$230.95	$231.00
Purchase #4	$154.81	12.269%	$173.8036	$173.80	$173.80	$173.80
Purchase #5	$196.58	7.373%	$211.0738	$211.07	$211.05	$211.10
Purchase #6	$112.52	12.873%	$127.0047	$127.00	$127.00	$127.00
Purchase #7	$194.34	5.475%	$204.9801	$204.98	$205.00	$205.00
7 purchase totals =	$998.14		$1,092.8968	$1,092.88	$1,092.90	$1,092.90