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	$152.82	5.279%	$160.8874	$160.89	$160.90	$160.90
Purchase #2	$11.37	9.779%	$12.4819	$12.48	$12.50	$12.50
Purchase #3	$89.69	10.111%	$98.7586	$98.76	$98.75	$98.80
Purchase #4	$159.59	7.853%	$172.1226	$172.12	$172.10	$172.10
Purchase #5	$194.50	8.707%	$211.4351	$211.44	$211.45	$211.40
Purchase #6	$204.33	6.695%	$218.0099	$218.01	$218.00	$218.00
Purchase #7	$188.45	12.312%	$211.652	$211.65	$211.65	$211.70
7 purchase totals =	$1,000.75		$1,085.3475	$1,085.35	$1,085.35	$1,085.40