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	$145.64	7.437%	$156.4712	$156.47	$156.45	$156.50
Purchase #2	$125.92	13.749%	$143.2327	$143.23	$143.25	$143.20
Purchase #3	$83.50	6.755%	$89.1404	$89.14	$89.15	$89.10
Purchase #4	$108.86	5.505%	$114.8527	$114.85	$114.85	$114.90
Purchase #5	$201.82	3.417%	$208.7162	$208.72	$208.70	$208.70
Purchase #6	$152.54	4.148%	$158.8674	$158.87	$158.85	$158.90
Purchase #7	$104.90	7.774%	$113.0549	$113.05	$113.05	$113.10
7 purchase totals =	$923.18		$984.3355	$984.33	$984.30	$984.40