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	$179.36	6.700%	$191.3771	$191.38	$191.40	$191.40
Purchase #2	$208.38	10.219%	$229.6744	$229.67	$229.65	$229.70
Purchase #3	$181.30	13.829%	$206.372	$206.37	$206.35	$206.40
Purchase #4	$179.34	6.797%	$191.5297	$191.53	$191.55	$191.50
Purchase #5	$35.87	10.737%	$39.7214	$39.72	$39.70	$39.70
Purchase #6	$128.25	13.191%	$145.1675	$145.17	$145.15	$145.20
Purchase #7	$19.97	3.213%	$20.6116	$20.61	$20.60	$20.60
7 purchase totals =	$932.47		$1,024.4537	$1,024.45	$1,024.40	$1,024.50