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	$196.38	7.289%	$210.6941	$210.69	$210.70	$210.70
Purchase #2	$107.83	3.139%	$111.2148	$111.21	$111.20	$111.20
Purchase #3	$63.48	6.386%	$67.5338	$67.53	$67.55	$67.50
Purchase #4	$188.58	4.168%	$196.44	$196.44	$196.45	$196.40
Purchase #5	$42.75	9.160%	$46.6659	$46.67	$46.65	$46.70
Purchase #6	$211.98	13.394%	$240.3726	$240.37	$240.35	$240.40
Purchase #7	$65.99	11.192%	$73.3756	$73.38	$73.40	$73.40
7 purchase totals =	$876.99		$946.2968	$946.29	$946.30	$946.30