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	$172.65	13.791%	$196.4602	$196.46	$196.45	$196.50
Purchase #2	$154.30	12.867%	$174.1538	$174.15	$174.15	$174.20
Purchase #3	$145.76	7.615%	$156.8596	$156.86	$156.85	$156.90
Purchase #4	$45.38	6.107%	$48.1514	$48.15	$48.15	$48.20
Purchase #5	$225.79	7.139%	$241.9091	$241.91	$241.90	$241.90
Purchase #6	$92.94	7.785%	$100.1754	$100.18	$100.20	$100.20
Purchase #7	$10.37	4.360%	$10.8221	$10.82	$10.80	$10.80
7 purchase totals =	$847.19		$928.5316	$928.53	$928.50	$928.70