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	$96.76	6.388%	$102.941	$102.94	$102.95	$102.90
Purchase #2	$188.46	4.365%	$196.6863	$196.69	$196.70	$196.70
Purchase #3	$38.50	11.139%	$42.7885	$42.79	$42.80	$42.80
Purchase #4	$123.48	11.631%	$137.842	$137.84	$137.85	$137.80
Purchase #5	$105.62	5.524%	$111.4544	$111.45	$111.45	$111.50
Purchase #6	$220.70	5.605%	$233.0702	$233.07	$233.05	$233.10
Purchase #7	$33.33	12.342%	$37.4436	$37.44	$37.45	$37.40
7 purchase totals =	$806.85		$862.2260	$862.22	$862.25	$862.20