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	$175.51	5.567%	$185.2806	$185.28	$185.30	$185.30
Purchase #2	$126.55	10.490%	$139.8251	$139.83	$139.85	$139.80
Purchase #3	$43.60	9.610%	$47.79	$47.79	$47.80	$47.80
Purchase #4	$247.32	10.700%	$273.7832	$273.78	$273.80	$273.80
Purchase #5	$37.64	3.174%	$38.8347	$38.83	$38.85	$38.80
Purchase #6	$176.47	5.277%	$185.7823	$185.78	$185.80	$185.80
Purchase #7	$223.52	5.519%	$235.8561	$235.86	$235.85	$235.90
7 purchase totals =	$1,030.61		$1,107.1520	$1,107.15	$1,107.25	$1,107.20