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	$83.88	9.360%	$91.7312	$91.73	$91.75	$91.70
Purchase #2	$202.83	9.682%	$222.468	$222.47	$222.45	$222.50
Purchase #3	$230.98	12.565%	$260.0026	$260.00	$260.00	$260.00
Purchase #4	$114.79	12.778%	$129.4579	$129.46	$129.45	$129.50
Purchase #5	$185.37	4.738%	$194.1528	$194.15	$194.15	$194.20
Purchase #6	$229.69	11.719%	$256.6074	$256.61	$256.60	$256.60
Purchase #7	$55.27	11.462%	$61.605	$61.61	$61.60	$61.60
7 purchase totals =	$1,102.81		$1,216.0249	$1,216.03	$1,216.00	$1,216.10