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	$180.82	5.659%	$191.0526	$191.05	$191.05	$191.10
Purchase #2	$198.62	13.485%	$225.4039	$225.40	$225.40	$225.40
Purchase #3	$95.56	5.512%	$100.8273	$100.83	$100.85	$100.80
Purchase #4	$208.52	12.174%	$233.9052	$233.91	$233.90	$233.90
Purchase #5	$51.75	5.119%	$54.3991	$54.40	$54.40	$54.40
Purchase #6	$188.32	5.315%	$198.3292	$198.33	$198.35	$198.30
Purchase #7	$23.27	12.355%	$26.145	$26.15	$26.15	$26.10
7 purchase totals =	$946.86		$1,030.0623	$1,030.07	$1,030.10	$1,030.00