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	$183.44	6.848%	$196.002	$196.00	$196.00	$196.00
Purchase #2	$236.72	5.517%	$249.7798	$249.78	$249.80	$249.80
Purchase #3	$166.67	10.133%	$183.5587	$183.56	$183.55	$183.60
Purchase #4	$159.37	4.589%	$166.6835	$166.68	$166.70	$166.70
Purchase #5	$124.53	7.436%	$133.7901	$133.79	$133.80	$133.80
Purchase #6	$229.46	12.754%	$258.7253	$258.73	$258.75	$258.70
Purchase #7	$129.34	11.706%	$144.4805	$144.48	$144.50	$144.50
7 purchase totals =	$1,229.53		$1,333.0199	$1,333.02	$1,333.10	$1,333.10