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	$241.45	3.752%	$250.5092	$250.51	$250.50	$250.50
Purchase #2	$125.92	4.231%	$131.2477	$131.25	$131.25	$131.20
Purchase #3	$10.41	6.307%	$11.0666	$11.07	$11.05	$11.10
Purchase #4	$26.72	6.568%	$28.475	$28.48	$28.50	$28.50
Purchase #5	$195.91	4.433%	$204.5947	$204.59	$204.60	$204.60
Purchase #6	$241.60	8.373%	$261.8292	$261.83	$261.85	$261.80
Purchase #7	$205.62	3.625%	$213.0737	$213.07	$213.05	$213.10
7 purchase totals =	$1,047.63		$1,100.7961	$1,100.80	$1,100.80	$1,100.80