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	$221.66	6.523%	$236.1189	$236.12	$236.10	$236.10
Purchase #2	$145.97	4.490%	$152.5241	$152.52	$152.50	$152.50
Purchase #3	$217.25	8.663%	$236.0704	$236.07	$236.05	$236.10
Purchase #4	$196.96	4.799%	$206.4121	$206.41	$206.40	$206.40
Purchase #5	$30.65	7.288%	$32.8838	$32.88	$32.90	$32.90
Purchase #6	$90.57	11.155%	$100.6731	$100.67	$100.65	$100.70
Purchase #7	$126.64	11.468%	$141.1631	$141.16	$141.15	$141.20
7 purchase totals =	$1,029.70		$1,105.8455	$1,105.83	$1,105.75	$1,105.90