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	$177.95	3.507%	$184.1907	$184.19	$184.20	$184.20
Purchase #2	$240.51	10.158%	$264.941	$264.94	$264.95	$264.90
Purchase #3	$178.59	11.620%	$199.3422	$199.34	$199.35	$199.30
Purchase #4	$83.99	7.308%	$90.128	$90.13	$90.15	$90.10
Purchase #5	$107.93	8.461%	$117.062	$117.06	$117.05	$117.10
Purchase #6	$60.69	11.160%	$67.463	$67.46	$67.45	$67.50
Purchase #7	$151.80	6.810%	$162.1376	$162.14	$162.15	$162.10
7 purchase totals =	$1,001.46		$1,085.2645	$1,085.26	$1,085.30	$1,085.20