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	$162.79	4.535%	$170.1725	$170.17	$170.15	$170.20
Purchase #2	$128.27	6.104%	$136.0996	$136.10	$136.10	$136.10
Purchase #3	$216.89	12.244%	$243.446	$243.45	$243.45	$243.40
Purchase #4	$37.32	12.702%	$42.0604	$42.06	$42.05	$42.10
Purchase #5	$143.28	5.830%	$151.6332	$151.63	$151.65	$151.60
Purchase #6	$219.67	12.577%	$247.2979	$247.30	$247.30	$247.30
Purchase #7	$165.83	7.833%	$178.8195	$178.82	$178.80	$178.80
7 purchase totals =	$1,074.05		$1,169.5291	$1,169.53	$1,169.50	$1,169.50