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	$198.91	7.512%	$213.8521	$213.85	$213.85	$213.90
Purchase #2	$92.71	7.371%	$99.5437	$99.54	$99.55	$99.50
Purchase #3	$135.83	4.156%	$141.4751	$141.48	$141.50	$141.50
Purchase #4	$5.58	10.551%	$6.1687	$6.17	$6.15	$6.20
Purchase #5	$164.91	4.224%	$171.8758	$171.88	$171.90	$171.90
Purchase #6	$208.40	6.446%	$221.8335	$221.83	$221.85	$221.80
Purchase #7	$44.93	3.318%	$46.4208	$46.42	$46.40	$46.40
7 purchase totals =	$851.27		$901.1697	$901.17	$901.20	$901.20