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	$184.53	4.617%	$193.0498	$193.05	$193.05	$193.00
Purchase #2	$206.49	9.361%	$225.8195	$225.82	$225.80	$225.80
Purchase #3	$169.98	10.182%	$187.2874	$187.29	$187.30	$187.30
Purchase #4	$88.73	10.627%	$98.1593	$98.16	$98.15	$98.20
Purchase #5	$95.37	11.223%	$106.0734	$106.07	$106.05	$106.10
Purchase #6	$72.89	13.451%	$82.6944	$82.69	$82.70	$82.70
Purchase #7	$155.47	10.343%	$171.5503	$171.55	$171.55	$171.60
7 purchase totals =	$973.46		$1,064.6341	$1,064.63	$1,064.60	$1,064.70