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	$22.71	12.510%	$25.551	$25.55	$25.55	$25.60
Purchase #2	$12.66	6.371%	$13.4666	$13.47	$13.45	$13.50
Purchase #3	$105.79	3.860%	$109.8735	$109.87	$109.85	$109.90
Purchase #4	$18.75	9.690%	$20.5669	$20.57	$20.55	$20.60
Purchase #5	$55.67	9.731%	$61.0872	$61.09	$61.10	$61.10
Purchase #6	$175.31	5.852%	$185.5691	$185.57	$185.55	$185.60
Purchase #7	$139.35	7.475%	$149.7664	$149.77	$149.75	$149.80
7 purchase totals =	$530.24		$565.8807	$565.89	$565.80	$566.10