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	$219.39	5.164%	$230.7193	$230.72	$230.70	$230.70
Purchase #2	$232.37	13.711%	$264.2303	$264.23	$264.25	$264.20
Purchase #3	$192.71	8.762%	$209.5953	$209.60	$209.60	$209.60
Purchase #4	$67.47	4.747%	$70.6728	$70.67	$70.65	$70.70
Purchase #5	$75.65	3.418%	$78.2357	$78.24	$78.25	$78.20
Purchase #6	$209.76	6.739%	$223.8957	$223.90	$223.90	$223.90
Purchase #7	$77.34	10.151%	$85.1908	$85.19	$85.20	$85.20
7 purchase totals =	$1,074.69		$1,162.5399	$1,162.55	$1,162.55	$1,162.50