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	$34.96	7.559%	$37.6026	$37.60	$37.60	$37.60
Purchase #2	$178.59	12.191%	$200.3619	$200.36	$200.35	$200.40
Purchase #3	$215.40	11.470%	$240.1064	$240.11	$240.10	$240.10
Purchase #4	$62.45	8.505%	$67.7614	$67.76	$67.75	$67.80
Purchase #5	$112.61	9.130%	$122.8913	$122.89	$122.90	$122.90
Purchase #6	$185.86	9.123%	$202.816	$202.82	$202.80	$202.80
Purchase #7	$187.38	11.789%	$209.4702	$209.47	$209.45	$209.50
7 purchase totals =	$977.25		$1,081.0098	$1,081.01	$1,080.95	$1,081.10