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	$54.48	8.366%	$59.0378	$59.04	$59.05	$59.00
Purchase #2	$41.78	4.150%	$43.5139	$43.51	$43.50	$43.50
Purchase #3	$186.62	4.857%	$195.6841	$195.68	$195.70	$195.70
Purchase #4	$246.30	10.344%	$271.7773	$271.78	$271.80	$271.80
Purchase #5	$77.52	6.212%	$82.3355	$82.34	$82.35	$82.30
Purchase #6	$234.45	3.791%	$243.338	$243.34	$243.35	$243.30
Purchase #7	$166.50	10.596%	$184.1423	$184.14	$184.15	$184.10
7 purchase totals =	$1,007.65		$1,079.8289	$1,079.83	$1,079.90	$1,079.70