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	$97.99	11.277%	$109.0403	$109.04	$109.05	$109.00
Purchase #2	$202.50	3.336%	$209.2554	$209.26	$209.25	$209.30
Purchase #3	$146.66	8.796%	$159.5602	$159.56	$159.55	$159.60
Purchase #4	$85.57	12.871%	$96.5837	$96.58	$96.60	$96.60
Purchase #5	$236.98	11.354%	$263.8867	$263.89	$263.90	$263.90
Purchase #6	$59.43	12.628%	$66.9348	$66.93	$66.95	$66.90
Purchase #7	$125.89	12.207%	$141.2574	$141.26	$141.25	$141.30
7 purchase totals =	$955.02		$1,046.5185	$1,046.52	$1,046.55	$1,046.60