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	$130.52	13.275%	$147.8465	$147.85	$147.85	$147.80
Purchase #2	$242.95	5.113%	$255.372	$255.37	$255.35	$255.40
Purchase #3	$99.89	13.851%	$113.7258	$113.73	$113.75	$113.70
Purchase #4	$168.53	12.834%	$190.1591	$190.16	$190.15	$190.20
Purchase #5	$181.56	5.362%	$191.2952	$191.30	$191.30	$191.30
Purchase #6	$169.54	11.410%	$188.8845	$188.88	$188.90	$188.90
Purchase #7	$70.66	12.319%	$79.3646	$79.36	$79.35	$79.40
7 purchase totals =	$1,063.65		$1,166.6477	$1,166.65	$1,166.65	$1,166.70