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	$132.34	3.399%	$136.8382	$136.84	$136.85	$136.80
Purchase #2	$181.70	5.347%	$191.4155	$191.42	$191.40	$191.40
Purchase #3	$221.73	9.665%	$243.1602	$243.16	$243.15	$243.20
Purchase #4	$130.95	4.326%	$136.6149	$136.61	$136.60	$136.60
Purchase #5	$65.27	10.151%	$71.8956	$71.90	$71.90	$71.90
Purchase #6	$247.46	6.697%	$264.0324	$264.03	$264.05	$264.00
Purchase #7	$122.37	7.788%	$131.9002	$131.90	$131.90	$131.90
7 purchase totals =	$1,101.82		$1,175.8570	$1,175.86	$1,175.85	$1,175.80