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	$148.47	11.823%	$166.0236	$166.02	$166.00	$166.00
Purchase #2	$119.87	11.622%	$133.8013	$133.80	$133.80	$133.80
Purchase #3	$182.71	7.443%	$196.3091	$196.31	$196.30	$196.30
Purchase #4	$147.53	10.379%	$162.8421	$162.84	$162.85	$162.80
Purchase #5	$161.96	12.218%	$181.7483	$181.75	$181.75	$181.70
Purchase #6	$172.61	10.775%	$191.2087	$191.21	$191.20	$191.20
Purchase #7	$18.63	11.626%	$20.7959	$20.80	$20.80	$20.80
7 purchase totals =	$951.78		$1,052.7290	$1,052.73	$1,052.70	$1,052.60