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	$225.98	8.464%	$245.1069	$245.11	$245.10	$245.10
Purchase #2	$214.29	11.229%	$238.3526	$238.35	$238.35	$238.40
Purchase #3	$54.52	5.122%	$57.3125	$57.31	$57.30	$57.30
Purchase #4	$247.86	8.652%	$269.3048	$269.30	$269.30	$269.30
Purchase #5	$21.76	4.700%	$22.7827	$22.78	$22.80	$22.80
Purchase #6	$63.53	7.822%	$68.4993	$68.50	$68.50	$68.50
Purchase #7	$89.60	11.812%	$100.1836	$100.18	$100.20	$100.20
7 purchase totals =	$917.54		$1,001.5424	$1,001.53	$1,001.55	$1,001.60