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	$101.85	3.551%	$105.4667	$105.47	$105.45	$105.50
Purchase #2	$141.84	12.871%	$160.0962	$160.10	$160.10	$160.10
Purchase #3	$92.69	7.526%	$99.6658	$99.67	$99.65	$99.70
Purchase #4	$162.56	10.663%	$179.8938	$179.89	$179.90	$179.90
Purchase #5	$203.76	13.270%	$230.799	$230.80	$230.80	$230.80
Purchase #6	$206.78	4.773%	$216.6496	$216.65	$216.65	$216.60
Purchase #7	$131.62	8.276%	$142.5129	$142.51	$142.50	$142.50
7 purchase totals =	$1,041.10		$1,135.0840	$1,135.09	$1,135.05	$1,135.10