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	$159.53	5.394%	$168.135	$168.14	$168.15	$168.10
Purchase #2	$73.86	3.488%	$76.4362	$76.44	$76.45	$76.40
Purchase #3	$27.64	10.198%	$30.4587	$30.46	$30.45	$30.50
Purchase #4	$62.79	5.313%	$66.126	$66.13	$66.15	$66.10
Purchase #5	$41.70	10.128%	$45.9234	$45.92	$45.90	$45.90
Purchase #6	$72.92	5.214%	$76.722	$76.72	$76.70	$76.70
Purchase #7	$98.79	12.840%	$111.4746	$111.47	$111.45	$111.50
7 purchase totals =	$537.23		$575.2759	$575.28	$575.25	$575.20