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	$179.34	9.612%	$196.5782	$196.58	$196.60	$196.60
Purchase #2	$44.39	4.601%	$46.4324	$46.43	$46.45	$46.40
Purchase #3	$44.34	3.366%	$45.8325	$45.83	$45.85	$45.80
Purchase #4	$233.66	9.862%	$256.7035	$256.70	$256.70	$256.70
Purchase #5	$193.26	5.341%	$203.582	$203.58	$203.60	$203.60
Purchase #6	$38.56	3.295%	$39.8306	$39.83	$39.85	$39.80
Purchase #7	$82.66	7.869%	$89.1645	$89.16	$89.15	$89.20
7 purchase totals =	$816.21		$878.1237	$878.11	$878.20	$878.10