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	$59.79	7.562%	$64.3113	$64.31	$64.30	$64.30
Purchase #2	$226.78	5.124%	$238.4002	$238.40	$238.40	$238.40
Purchase #3	$210.38	11.812%	$235.2301	$235.23	$235.25	$235.20
Purchase #4	$199.54	4.287%	$208.0943	$208.09	$208.10	$208.10
Purchase #5	$99.50	11.556%	$110.9982	$111.00	$111.00	$111.00
Purchase #6	$129.72	13.421%	$147.1297	$147.13	$147.15	$147.10
Purchase #7	$137.59	9.366%	$150.4767	$150.48	$150.50	$150.50
7 purchase totals =	$1,063.30		$1,154.6405	$1,154.64	$1,154.70	$1,154.60