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	$220.77	7.382%	$237.0672	$237.07	$237.05	$237.10
Purchase #2	$75.70	8.374%	$82.0391	$82.04	$82.05	$82.00
Purchase #3	$57.97	13.470%	$65.7786	$65.78	$65.80	$65.80
Purchase #4	$198.54	5.176%	$208.8164	$208.82	$208.80	$208.80
Purchase #5	$92.64	8.194%	$100.2309	$100.23	$100.25	$100.20
Purchase #6	$145.42	4.466%	$151.9145	$151.91	$151.90	$151.90
Purchase #7	$70.38	11.538%	$78.5004	$78.50	$78.50	$78.50
7 purchase totals =	$861.42		$924.3471	$924.35	$924.35	$924.30