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	$65.50	10.588%	$72.4351	$72.44	$72.45	$72.40
Purchase #2	$215.93	3.726%	$223.9756	$223.98	$224.00	$224.00
Purchase #3	$42.83	4.786%	$44.8798	$44.88	$44.90	$44.90
Purchase #4	$114.56	13.682%	$130.2341	$130.23	$130.25	$130.20
Purchase #5	$67.83	6.519%	$72.2518	$72.25	$72.25	$72.30
Purchase #6	$57.87	11.521%	$64.5372	$64.54	$64.55	$64.50
Purchase #7	$201.43	4.202%	$209.8941	$209.89	$209.90	$209.90
7 purchase totals =	$765.95		$818.2077	$818.21	$818.30	$818.20