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	$194.50	4.279%	$202.8227	$202.82	$202.80	$202.80
Purchase #2	$38.65	10.855%	$42.8455	$42.85	$42.85	$42.80
Purchase #3	$206.81	7.771%	$222.8812	$222.88	$222.90	$222.90
Purchase #4	$129.40	11.621%	$144.4376	$144.44	$144.45	$144.40
Purchase #5	$41.97	3.363%	$43.3815	$43.38	$43.40	$43.40
Purchase #6	$99.65	12.275%	$111.882	$111.88	$111.90	$111.90
Purchase #7	$234.82	13.447%	$266.3962	$266.40	$266.40	$266.40
7 purchase totals =	$945.80		$1,034.6467	$1,034.65	$1,034.70	$1,034.60