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	$10.89	8.618%	$11.8285	$11.83	$11.85	$11.80
Purchase #2	$61.50	9.530%	$67.361	$67.36	$67.35	$67.40
Purchase #3	$157.57	11.563%	$175.7898	$175.79	$175.80	$175.80
Purchase #4	$242.29	11.648%	$270.5119	$270.51	$270.50	$270.50
Purchase #5	$78.89	9.713%	$86.5526	$86.55	$86.55	$86.60
Purchase #6	$191.95	11.685%	$214.3794	$214.38	$214.40	$214.40
Purchase #7	$219.80	10.199%	$242.2174	$242.22	$242.20	$242.20
7 purchase totals =	$962.89		$1,068.6406	$1,068.64	$1,068.65	$1,068.70