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	$219.98	13.790%	$250.3152	$250.32	$250.30	$250.30
Purchase #2	$215.54	12.580%	$242.6549	$242.65	$242.65	$242.70
Purchase #3	$155.50	9.261%	$169.9009	$169.90	$169.90	$169.90
Purchase #4	$198.39	12.225%	$222.6432	$222.64	$222.65	$222.60
Purchase #5	$146.45	10.717%	$162.145	$162.15	$162.15	$162.10
Purchase #6	$69.82	7.165%	$74.8226	$74.82	$74.80	$74.80
Purchase #7	$222.67	11.618%	$248.5398	$248.54	$248.55	$248.50
7 purchase totals =	$1,228.35		$1,371.0216	$1,371.02	$1,371.00	$1,370.90