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	$164.66	6.538%	$175.4255	$175.43	$175.45	$175.40
Purchase #2	$136.40	6.723%	$145.5702	$145.57	$145.55	$145.60
Purchase #3	$152.54	10.258%	$168.1876	$168.19	$168.20	$168.20
Purchase #4	$114.44	11.751%	$127.8878	$127.89	$127.90	$127.90
Purchase #5	$53.85	9.515%	$58.9738	$58.97	$58.95	$59.00
Purchase #6	$192.86	5.345%	$203.1684	$203.17	$203.15	$203.20
Purchase #7	$64.55	10.217%	$71.1451	$71.15	$71.15	$71.10
7 purchase totals =	$879.30		$950.3584	$950.37	$950.35	$950.40