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	$187.47	8.642%	$203.6712	$203.67	$203.65	$203.70
Purchase #2	$63.77	13.293%	$72.2469	$72.25	$72.25	$72.20
Purchase #3	$33.82	11.109%	$37.5771	$37.58	$37.60	$37.60
Purchase #4	$233.81	7.267%	$250.801	$250.80	$250.80	$250.80
Purchase #5	$178.49	9.130%	$194.7861	$194.79	$194.80	$194.80
Purchase #6	$190.50	13.800%	$216.789	$216.79	$216.80	$216.80
Purchase #7	$47.83	13.184%	$54.1359	$54.14	$54.15	$54.10
7 purchase totals =	$935.69		$1,030.0072	$1,030.02	$1,030.05	$1,030.00