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	$148.29	13.689%	$168.5894	$168.59	$168.60	$168.60
Purchase #2	$48.59	11.771%	$54.3095	$54.31	$54.30	$54.30
Purchase #3	$66.61	8.201%	$72.0727	$72.07	$72.05	$72.10
Purchase #4	$222.68	9.199%	$243.1643	$243.16	$243.15	$243.20
Purchase #5	$62.89	3.672%	$65.1993	$65.20	$65.20	$65.20
Purchase #6	$96.75	9.832%	$106.2625	$106.26	$106.25	$106.30
Purchase #7	$247.96	11.599%	$276.7209	$276.72	$276.70	$276.70
7 purchase totals =	$893.77		$986.3186	$986.31	$986.25	$986.40