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	$206.97	12.609%	$233.0668	$233.07	$233.05	$233.10
Purchase #2	$215.72	3.757%	$223.8246	$223.82	$223.80	$223.80
Purchase #3	$77.65	10.258%	$85.6153	$85.62	$85.60	$85.60
Purchase #4	$72.33	11.219%	$80.4447	$80.44	$80.45	$80.40
Purchase #5	$200.90	3.703%	$208.3393	$208.34	$208.35	$208.30
Purchase #6	$103.61	7.700%	$111.588	$111.59	$111.60	$111.60
Purchase #7	$116.86	3.136%	$120.5247	$120.52	$120.50	$120.50
7 purchase totals =	$994.04		$1,063.4034	$1,063.40	$1,063.35	$1,063.30