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	$47.60	5.151%	$50.0519	$50.05	$50.05	$50.10
Purchase #2	$209.76	3.685%	$217.4897	$217.49	$217.50	$217.50
Purchase #3	$131.45	12.596%	$148.0074	$148.01	$148.00	$148.00
Purchase #4	$147.90	3.753%	$153.4507	$153.45	$153.45	$153.50
Purchase #5	$146.54	9.848%	$160.9713	$160.97	$160.95	$161.00
Purchase #6	$193.65	6.769%	$206.7582	$206.76	$206.75	$206.80
Purchase #7	$75.88	9.223%	$82.8784	$82.88	$82.90	$82.90
7 purchase totals =	$952.78		$1,019.6076	$1,019.61	$1,019.60	$1,019.80