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	$189.29	7.191%	$202.9018	$202.90	$202.90	$202.90
Purchase #2	$198.41	9.804%	$217.8621	$217.86	$217.85	$217.90
Purchase #3	$152.60	13.188%	$172.7249	$172.72	$172.70	$172.70
Purchase #4	$134.46	13.345%	$152.4037	$152.40	$152.40	$152.40
Purchase #5	$41.94	5.411%	$44.2094	$44.21	$44.20	$44.20
Purchase #6	$243.51	10.541%	$269.1784	$269.18	$269.20	$269.20
Purchase #7	$180.55	11.113%	$200.6145	$200.61	$200.60	$200.60
7 purchase totals =	$1,140.76		$1,259.8948	$1,259.88	$1,259.85	$1,259.90