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	$152.47	11.804%	$170.4676	$170.47	$170.45	$170.50
Purchase #2	$124.65	5.682%	$131.7326	$131.73	$131.75	$131.70
Purchase #3	$95.39	5.373%	$100.5153	$100.52	$100.50	$100.50
Purchase #4	$87.64	9.575%	$96.0315	$96.03	$96.05	$96.00
Purchase #5	$162.91	5.773%	$172.3148	$172.31	$172.30	$172.30
Purchase #6	$142.45	5.516%	$150.3075	$150.31	$150.30	$150.30
Purchase #7	$197.90	7.570%	$212.881	$212.88	$212.90	$212.90
7 purchase totals =	$963.41		$1,034.2503	$1,034.25	$1,034.25	$1,034.20