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	$137.26	10.272%	$151.3593	$151.36	$151.35	$151.40
Purchase #2	$40.84	10.212%	$45.0106	$45.01	$45.00	$45.00
Purchase #3	$198.85	7.372%	$213.5092	$213.51	$213.50	$213.50
Purchase #4	$140.50	8.778%	$152.8331	$152.83	$152.85	$152.80
Purchase #5	$43.75	13.841%	$49.8054	$49.81	$49.80	$49.80
Purchase #6	$89.85	10.799%	$99.5529	$99.55	$99.55	$99.60
Purchase #7	$211.69	8.423%	$229.5206	$229.52	$229.50	$229.50
7 purchase totals =	$862.74		$941.5911	$941.59	$941.55	$941.60