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	$185.66	7.548%	$199.6736	$199.67	$199.65	$199.70
Purchase #2	$186.53	11.636%	$208.2346	$208.23	$208.25	$208.20
Purchase #3	$59.97	11.747%	$67.0147	$67.01	$67.00	$67.00
Purchase #4	$50.88	5.290%	$53.5716	$53.57	$53.55	$53.60
Purchase #5	$13.84	6.109%	$14.6855	$14.69	$14.70	$14.70
Purchase #6	$108.52	6.272%	$115.3264	$115.33	$115.35	$115.30
Purchase #7	$89.67	11.864%	$100.3084	$100.31	$100.30	$100.30
7 purchase totals =	$695.07		$758.8148	$758.81	$758.80	$758.80