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	$36.74	10.632%	$40.6462	$40.65	$40.65	$40.60
Purchase #2	$186.44	12.835%	$210.3696	$210.37	$210.35	$210.40
Purchase #3	$93.51	7.567%	$100.5859	$100.59	$100.60	$100.60
Purchase #4	$185.80	7.603%	$199.9264	$199.93	$199.95	$199.90
Purchase #5	$157.57	13.588%	$178.9806	$178.98	$179.00	$179.00
Purchase #6	$189.46	12.557%	$213.2505	$213.25	$213.25	$213.30
Purchase #7	$116.35	12.442%	$130.8263	$130.83	$130.85	$130.80
7 purchase totals =	$965.87		$1,074.5855	$1,074.60	$1,074.65	$1,074.60