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	$217.38	11.234%	$241.8005	$241.80	$241.80	$241.80
Purchase #2	$178.46	12.399%	$200.5873	$200.59	$200.60	$200.60
Purchase #3	$147.38	7.366%	$158.236	$158.24	$158.25	$158.20
Purchase #4	$122.29	12.289%	$137.3182	$137.32	$137.30	$137.30
Purchase #5	$146.48	9.171%	$159.9137	$159.91	$159.90	$159.90
Purchase #6	$217.69	10.844%	$241.2963	$241.30	$241.30	$241.30
Purchase #7	$37.74	6.756%	$40.2897	$40.29	$40.30	$40.30
7 purchase totals =	$1,067.42		$1,179.4417	$1,179.45	$1,179.45	$1,179.40