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	$203.36	13.482%	$230.777	$230.78	$230.80	$230.80
Purchase #2	$246.66	3.741%	$255.8876	$255.89	$255.90	$255.90
Purchase #3	$80.32	10.289%	$88.5841	$88.58	$88.60	$88.60
Purchase #4	$154.27	13.837%	$175.6163	$175.62	$175.60	$175.60
Purchase #5	$28.73	7.653%	$30.9287	$30.93	$30.95	$30.90
Purchase #6	$31.27	5.134%	$32.8754	$32.88	$32.90	$32.90
Purchase #7	$210.74	5.287%	$221.8818	$221.88	$221.90	$221.90
7 purchase totals =	$955.35		$1,036.5509	$1,036.56	$1,036.65	$1,036.60