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	$143.90	5.241%	$151.4418	$151.44	$151.45	$151.40
Purchase #2	$21.74	3.646%	$22.5326	$22.53	$22.55	$22.50
Purchase #3	$48.86	3.514%	$50.5769	$50.58	$50.60	$50.60
Purchase #4	$226.80	7.473%	$243.7488	$243.75	$243.75	$243.70
Purchase #5	$162.75	11.513%	$181.4874	$181.49	$181.50	$181.50
Purchase #6	$186.76	13.599%	$212.1575	$212.16	$212.15	$212.20
Purchase #7	$72.71	11.257%	$80.895	$80.90	$80.90	$80.90
7 purchase totals =	$863.52		$942.8400	$942.85	$942.90	$942.80