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	$33.89	11.481%	$37.7809	$37.78	$37.80	$37.80
Purchase #2	$235.86	8.367%	$255.5944	$255.59	$255.60	$255.60
Purchase #3	$72.77	7.381%	$78.1412	$78.14	$78.15	$78.10
Purchase #4	$180.94	8.414%	$196.1643	$196.16	$196.15	$196.20
Purchase #5	$154.72	9.570%	$169.5267	$169.53	$169.55	$169.50
Purchase #6	$119.81	13.311%	$135.7579	$135.76	$135.75	$135.80
Purchase #7	$216.92	13.185%	$245.5209	$245.52	$245.50	$245.50
7 purchase totals =	$1,014.91		$1,118.4863	$1,118.48	$1,118.50	$1,118.50