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	$153.91	13.487%	$174.6678	$174.67	$174.65	$174.70
Purchase #2	$182.67	6.477%	$194.5015	$194.50	$194.50	$194.50
Purchase #3	$169.42	11.165%	$188.3357	$188.34	$188.35	$188.30
Purchase #4	$29.58	11.694%	$33.0391	$33.04	$33.05	$33.00
Purchase #5	$91.42	6.225%	$97.1109	$97.11	$97.10	$97.10
Purchase #6	$137.68	6.619%	$146.793	$146.79	$146.80	$146.80
Purchase #7	$181.59	8.187%	$196.4568	$196.46	$196.45	$196.50
7 purchase totals =	$946.27		$1,030.9048	$1,030.91	$1,030.90	$1,030.90