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	$181.30	5.281%	$190.8745	$190.87	$190.85	$190.90
Purchase #2	$37.53	6.478%	$39.9612	$39.96	$39.95	$40.00
Purchase #3	$18.41	10.416%	$20.3276	$20.33	$20.35	$20.30
Purchase #4	$197.82	6.306%	$210.2945	$210.29	$210.30	$210.30
Purchase #5	$176.57	11.199%	$196.3441	$196.34	$196.35	$196.30
Purchase #6	$69.89	11.336%	$77.8127	$77.81	$77.80	$77.80
Purchase #7	$113.38	8.771%	$123.3246	$123.32	$123.30	$123.30
7 purchase totals =	$794.90		$858.9392	$858.92	$858.90	$858.90