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	$171.57	11.809%	$191.8307	$191.83	$191.85	$191.80
Purchase #2	$225.57	11.704%	$251.9707	$251.97	$251.95	$252.00
Purchase #3	$113.94	8.467%	$123.5873	$123.59	$123.60	$123.60
Purchase #4	$92.25	8.873%	$100.4353	$100.44	$100.45	$100.40
Purchase #5	$142.59	13.168%	$161.3663	$161.37	$161.35	$161.40
Purchase #6	$223.55	10.382%	$246.759	$246.76	$246.75	$246.80
Purchase #7	$72.69	7.199%	$77.923	$77.92	$77.90	$77.90
7 purchase totals =	$1,042.16		$1,153.8723	$1,153.88	$1,153.85	$1,153.90