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	$189.61	7.773%	$204.3484	$204.35	$204.35	$204.30
Purchase #2	$137.56	10.156%	$151.5306	$151.53	$151.55	$151.50
Purchase #3	$138.43	9.423%	$151.4743	$151.47	$151.45	$151.50
Purchase #4	$165.50	13.672%	$188.1272	$188.13	$188.15	$188.10
Purchase #5	$233.83	13.355%	$265.058	$265.06	$265.05	$265.10
Purchase #6	$164.92	9.647%	$180.8298	$180.83	$180.85	$180.80
Purchase #7	$37.51	7.679%	$40.3904	$40.39	$40.40	$40.40
7 purchase totals =	$1,067.36		$1,181.7587	$1,181.76	$1,181.80	$1,181.70