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	$191.64	8.858%	$208.6155	$208.62	$208.60	$208.60
Purchase #2	$130.85	7.683%	$140.9032	$140.90	$140.90	$140.90
Purchase #3	$42.83	13.647%	$48.675	$48.68	$48.70	$48.70
Purchase #4	$173.73	9.246%	$189.7931	$189.79	$189.80	$189.80
Purchase #5	$47.53	10.685%	$52.6086	$52.61	$52.60	$52.60
Purchase #6	$223.46	11.393%	$248.9188	$248.92	$248.90	$248.90
Purchase #7	$174.34	9.571%	$191.0261	$191.03	$191.05	$191.00
7 purchase totals =	$984.38		$1,080.5403	$1,080.55	$1,080.55	$1,080.50