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	$136.59	7.845%	$147.3055	$147.31	$147.30	$147.30
Purchase #2	$59.57	5.165%	$62.6468	$62.65	$62.65	$62.60
Purchase #3	$166.77	9.363%	$182.3847	$182.38	$182.40	$182.40
Purchase #4	$64.31	11.851%	$71.9314	$71.93	$71.95	$71.90
Purchase #5	$34.38	7.714%	$37.0321	$37.03	$37.05	$37.00
Purchase #6	$79.53	7.463%	$85.4653	$85.47	$85.45	$85.50
Purchase #7	$90.50	4.487%	$94.5607	$94.56	$94.55	$94.60
7 purchase totals =	$631.65		$681.3265	$681.33	$681.35	$681.30