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	$39.68	5.268%	$41.7703	$41.77	$41.75	$41.80
Purchase #2	$90.28	10.279%	$99.5599	$99.56	$99.55	$99.60
Purchase #3	$134.29	5.337%	$141.4571	$141.46	$141.45	$141.50
Purchase #4	$167.48	3.132%	$172.7255	$172.73	$172.75	$172.70
Purchase #5	$129.89	12.634%	$146.3003	$146.30	$146.30	$146.30
Purchase #6	$242.91	4.147%	$252.9835	$252.98	$253.00	$253.00
Purchase #7	$142.88	3.654%	$148.1008	$148.10	$148.10	$148.10
7 purchase totals =	$947.41		$1,002.8974	$1,002.90	$1,002.90	$1,003.00