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	$107.92	9.862%	$118.5631	$118.56	$118.55	$118.60
Purchase #2	$158.27	7.230%	$169.7129	$169.71	$169.70	$169.70
Purchase #3	$155.66	6.359%	$165.5584	$165.56	$165.55	$165.60
Purchase #4	$108.54	13.609%	$123.3112	$123.31	$123.30	$123.30
Purchase #5	$136.80	5.625%	$144.495	$144.50	$144.50	$144.50
Purchase #6	$82.54	6.618%	$88.0025	$88.00	$88.00	$88.00
Purchase #7	$206.27	9.419%	$225.6986	$225.70	$225.70	$225.70
7 purchase totals =	$956.00		$1,035.3417	$1,035.34	$1,035.30	$1,035.40