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	$225.48	12.196%	$252.9795	$252.98	$253.00	$253.00
Purchase #2	$93.90	4.831%	$98.4363	$98.44	$98.45	$98.40
Purchase #3	$93.77	6.128%	$99.5162	$99.52	$99.50	$99.50
Purchase #4	$152.35	13.279%	$172.5806	$172.58	$172.60	$172.60
Purchase #5	$182.46	3.755%	$189.3114	$189.31	$189.30	$189.30
Purchase #6	$156.73	5.363%	$165.1354	$165.14	$165.15	$165.10
Purchase #7	$105.75	10.298%	$116.6401	$116.64	$116.65	$116.60
7 purchase totals =	$1,010.44		$1,094.5995	$1,094.61	$1,094.65	$1,094.50