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	$209.25	4.501%	$218.6683	$218.67	$218.65	$218.70
Purchase #2	$80.63	11.433%	$89.8484	$89.85	$89.85	$89.80
Purchase #3	$7.30	4.365%	$7.6186	$7.62	$7.60	$7.60
Purchase #4	$223.70	4.576%	$233.9365	$233.94	$233.95	$233.90
Purchase #5	$47.32	5.794%	$50.0617	$50.06	$50.05	$50.10
Purchase #6	$135.73	7.869%	$146.4106	$146.41	$146.40	$146.40
Purchase #7	$52.29	10.851%	$57.964	$57.96	$57.95	$58.00
7 purchase totals =	$756.22		$804.5081	$804.51	$804.45	$804.50