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	$232.31	12.833%	$262.1223	$262.12	$262.10	$262.10
Purchase #2	$83.64	7.304%	$89.7491	$89.75	$89.75	$89.70
Purchase #3	$51.77	4.586%	$54.1442	$54.14	$54.15	$54.10
Purchase #4	$186.53	7.474%	$200.4713	$200.47	$200.45	$200.50
Purchase #5	$133.69	9.579%	$146.4962	$146.50	$146.50	$146.50
Purchase #6	$219.94	3.558%	$227.7655	$227.77	$227.75	$227.80
Purchase #7	$92.72	13.461%	$105.201	$105.20	$105.20	$105.20
7 purchase totals =	$1,000.60		$1,085.9496	$1,085.95	$1,085.90	$1,085.90