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	$223.70	10.612%	$247.439	$247.44	$247.45	$247.40
Purchase #2	$87.49	12.360%	$98.3038	$98.30	$98.30	$98.30
Purchase #3	$119.31	10.492%	$131.828	$131.83	$131.85	$131.80
Purchase #4	$171.82	5.862%	$181.8921	$181.89	$181.90	$181.90
Purchase #5	$6.33	11.450%	$7.0548	$7.05	$7.05	$7.10
Purchase #6	$166.45	5.399%	$175.4366	$175.44	$175.45	$175.40
Purchase #7	$246.45	8.429%	$267.2233	$267.22	$267.20	$267.20
7 purchase totals =	$1,021.55		$1,109.1776	$1,109.17	$1,109.20	$1,109.10