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	$46.33	5.681%	$48.962	$48.96	$48.95	$49.00
Purchase #2	$119.33	11.659%	$133.2427	$133.24	$133.25	$133.20
Purchase #3	$82.71	9.508%	$90.5741	$90.57	$90.55	$90.60
Purchase #4	$25.51	7.310%	$27.3748	$27.37	$27.35	$27.40
Purchase #5	$197.46	8.652%	$214.5442	$214.54	$214.55	$214.50
Purchase #6	$206.31	7.426%	$221.6306	$221.63	$221.65	$221.60
Purchase #7	$101.73	9.437%	$111.3303	$111.33	$111.35	$111.30
7 purchase totals =	$779.38		$847.6587	$847.64	$847.65	$847.60