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	$167.72	11.182%	$186.4745	$186.47	$186.45	$186.50
Purchase #2	$219.75	10.532%	$242.8941	$242.89	$242.90	$242.90
Purchase #3	$247.26	4.383%	$258.0974	$258.10	$258.10	$258.10
Purchase #4	$115.34	9.268%	$126.0297	$126.03	$126.05	$126.00
Purchase #5	$89.31	7.272%	$95.8046	$95.80	$95.80	$95.80
Purchase #6	$129.90	5.397%	$136.9107	$136.91	$136.90	$136.90
Purchase #7	$43.38	11.267%	$48.2676	$48.27	$48.25	$48.30
7 purchase totals =	$1,012.66		$1,094.4786	$1,094.47	$1,094.45	$1,094.50