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	$9.34	12.568%	$10.5139	$10.51	$10.50	$10.50
Purchase #2	$75.40	4.663%	$78.9159	$78.92	$78.90	$78.90
Purchase #3	$208.60	5.372%	$219.806	$219.81	$219.80	$219.80
Purchase #4	$85.45	4.316%	$89.138	$89.14	$89.15	$89.10
Purchase #5	$195.72	10.621%	$216.5074	$216.51	$216.50	$216.50
Purchase #6	$91.62	10.441%	$101.186	$101.19	$101.20	$101.20
Purchase #7	$44.36	5.215%	$46.6734	$46.67	$46.65	$46.70
7 purchase totals =	$710.49		$762.7406	$762.75	$762.70	$762.70