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	$78.94	13.858%	$89.8795	$89.88	$89.90	$89.90
Purchase #2	$26.61	9.138%	$29.0416	$29.04	$29.05	$29.00
Purchase #3	$142.99	6.253%	$151.9312	$151.93	$151.95	$151.90
Purchase #4	$104.57	4.740%	$109.5266	$109.53	$109.55	$109.50
Purchase #5	$146.76	12.580%	$165.2224	$165.22	$165.20	$165.20
Purchase #6	$212.59	4.661%	$222.4988	$222.50	$222.50	$222.50
Purchase #7	$226.30	13.185%	$256.1377	$256.14	$256.15	$256.10
7 purchase totals =	$938.76		$1,024.2378	$1,024.24	$1,024.30	$1,024.10