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	$212.99	4.420%	$222.4042	$222.40	$222.40	$222.40
Purchase #2	$185.46	6.154%	$196.8732	$196.87	$196.85	$196.90
Purchase #3	$39.84	5.857%	$42.1734	$42.17	$42.15	$42.20
Purchase #4	$221.79	5.715%	$234.4653	$234.47	$234.45	$234.50
Purchase #5	$189.51	3.681%	$196.4859	$196.49	$196.50	$196.50
Purchase #6	$121.37	7.630%	$130.6305	$130.63	$130.65	$130.60
Purchase #7	$82.79	13.766%	$94.1869	$94.19	$94.20	$94.20
7 purchase totals =	$1,053.75		$1,117.2194	$1,117.22	$1,117.20	$1,117.30