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	$118.56	5.292%	$124.8342	$124.83	$124.85	$124.80
Purchase #2	$37.28	6.406%	$39.6682	$39.67	$39.65	$39.70
Purchase #3	$151.29	5.830%	$160.1102	$160.11	$160.10	$160.10
Purchase #4	$92.32	8.589%	$100.2494	$100.25	$100.25	$100.20
Purchase #5	$179.91	9.261%	$196.5715	$196.57	$196.55	$196.60
Purchase #6	$163.48	5.169%	$171.9303	$171.93	$171.95	$171.90
Purchase #7	$95.25	12.668%	$107.3163	$107.32	$107.30	$107.30
7 purchase totals =	$838.09		$900.6801	$900.68	$900.65	$900.60