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	$143.83	5.782%	$152.1463	$152.15	$152.15	$152.10
Purchase #2	$231.90	9.185%	$253.2	$253.20	$253.20	$253.20
Purchase #3	$89.39	3.501%	$92.5195	$92.52	$92.50	$92.50
Purchase #4	$203.64	11.181%	$226.409	$226.41	$226.40	$226.40
Purchase #5	$132.59	4.798%	$138.9517	$138.95	$138.95	$139.00
Purchase #6	$103.27	4.740%	$108.165	$108.17	$108.15	$108.20
Purchase #7	$206.97	8.862%	$225.3117	$225.31	$225.30	$225.30
7 purchase totals =	$1,111.59		$1,196.7032	$1,196.71	$1,196.65	$1,196.70