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	$88.77	12.829%	$100.1583	$100.16	$100.15	$100.20
Purchase #2	$96.82	12.647%	$109.0648	$109.06	$109.05	$109.10
Purchase #3	$201.70	4.371%	$210.5163	$210.52	$210.50	$210.50
Purchase #4	$91.81	12.791%	$103.5534	$103.55	$103.55	$103.60
Purchase #5	$241.67	12.821%	$272.6545	$272.65	$272.65	$272.70
Purchase #6	$117.56	10.680%	$130.1154	$130.12	$130.10	$130.10
Purchase #7	$100.43	5.432%	$105.8854	$105.89	$105.90	$105.90
7 purchase totals =	$938.76		$1,031.9481	$1,031.95	$1,031.90	$1,032.10