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	$52.33	12.862%	$59.0607	$59.06	$59.05	$59.10
Purchase #2	$40.98	10.818%	$45.4132	$45.41	$45.40	$45.40
Purchase #3	$234.64	13.844%	$267.1236	$267.12	$267.10	$267.10
Purchase #4	$28.37	4.347%	$29.6032	$29.60	$29.60	$29.60
Purchase #5	$249.44	8.781%	$271.3433	$271.34	$271.35	$271.30
Purchase #6	$222.49	10.575%	$246.0183	$246.02	$246.00	$246.00
Purchase #7	$127.89	5.214%	$134.5582	$134.56	$134.55	$134.60
7 purchase totals =	$956.14		$1,053.1205	$1,053.11	$1,053.05	$1,053.10