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	$186.83	10.373%	$206.2099	$206.21	$206.20	$206.20
Purchase #2	$182.37	11.829%	$203.9425	$203.94	$203.95	$203.90
Purchase #3	$30.29	6.533%	$32.2688	$32.27	$32.25	$32.30
Purchase #4	$204.37	10.381%	$225.5856	$225.59	$225.60	$225.60
Purchase #5	$38.71	9.521%	$42.3956	$42.40	$42.40	$42.40
Purchase #6	$202.85	9.748%	$222.6238	$222.62	$222.60	$222.60
Purchase #7	$131.46	12.269%	$147.5888	$147.59	$147.60	$147.60
7 purchase totals =	$976.88		$1,080.6150	$1,080.62	$1,080.60	$1,080.60