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	$170.89	13.829%	$194.5224	$194.52	$194.50	$194.50
Purchase #2	$42.39	3.477%	$43.8639	$43.86	$43.85	$43.90
Purchase #3	$173.40	13.181%	$196.2559	$196.26	$196.25	$196.30
Purchase #4	$33.73	9.289%	$36.8632	$36.86	$36.85	$36.90
Purchase #5	$193.52	5.709%	$204.5681	$204.57	$204.55	$204.60
Purchase #6	$25.66	12.551%	$28.8806	$28.88	$28.90	$28.90
Purchase #7	$245.76	11.731%	$274.5901	$274.59	$274.60	$274.60
7 purchase totals =	$885.35		$979.5442	$979.54	$979.50	$979.70