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	$50.33	5.407%	$53.0513	$53.05	$53.05	$53.10
Purchase #2	$150.85	3.810%	$156.5974	$156.60	$156.60	$156.60
Purchase #3	$55.30	10.523%	$61.1192	$61.12	$61.10	$61.10
Purchase #4	$29.94	7.225%	$32.1032	$32.10	$32.10	$32.10
Purchase #5	$129.92	5.178%	$136.6473	$136.65	$136.65	$136.60
Purchase #6	$81.44	7.576%	$87.6099	$87.61	$87.60	$87.60
Purchase #7	$64.55	11.220%	$71.7925	$71.79	$71.80	$71.80
7 purchase totals =	$562.33		$598.9208	$598.92	$598.90	$598.90