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	$171.88	12.257%	$192.9473	$192.95	$192.95	$192.90
Purchase #2	$75.76	11.433%	$84.4216	$84.42	$84.40	$84.40
Purchase #3	$39.42	3.650%	$40.8588	$40.86	$40.85	$40.90
Purchase #4	$45.34	11.594%	$50.5967	$50.60	$50.60	$50.60
Purchase #5	$120.36	3.842%	$124.9842	$124.98	$125.00	$125.00
Purchase #6	$146.33	12.724%	$164.949	$164.95	$164.95	$164.90
Purchase #7	$74.76	10.308%	$82.4663	$82.47	$82.45	$82.50
7 purchase totals =	$673.85		$741.2239	$741.23	$741.20	$741.20