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	$248.83	6.514%	$265.0388	$265.04	$265.05	$265.00
Purchase #2	$56.92	8.156%	$61.5624	$61.56	$61.55	$61.60
Purchase #3	$83.81	11.173%	$93.1741	$93.17	$93.15	$93.20
Purchase #4	$75.96	3.815%	$78.8579	$78.86	$78.85	$78.90
Purchase #5	$111.52	10.578%	$123.3166	$123.32	$123.30	$123.30
Purchase #6	$194.82	8.807%	$211.9778	$211.98	$212.00	$212.00
Purchase #7	$199.50	9.733%	$218.9173	$218.92	$218.90	$218.90
7 purchase totals =	$971.36		$1,052.8449	$1,052.85	$1,052.80	$1,052.90