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	$177.40	11.625%	$198.0228	$198.02	$198.00	$198.00
Purchase #2	$92.48	6.478%	$98.4709	$98.47	$98.45	$98.50
Purchase #3	$193.44	9.776%	$212.3507	$212.35	$212.35	$212.40
Purchase #4	$40.41	12.573%	$45.4907	$45.49	$45.50	$45.50
Purchase #5	$150.67	6.822%	$160.9487	$160.95	$160.95	$160.90
Purchase #6	$146.51	9.317%	$160.1603	$160.16	$160.15	$160.20
Purchase #7	$78.47	5.117%	$82.4853	$82.49	$82.50	$82.50
7 purchase totals =	$879.38		$957.9294	$957.93	$957.90	$958.00