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	$47.56	6.702%	$50.7475	$50.75	$50.75	$50.70
Purchase #2	$41.79	7.853%	$45.0718	$45.07	$45.05	$45.10
Purchase #3	$100.73	5.560%	$106.3306	$106.33	$106.35	$106.30
Purchase #4	$81.54	10.114%	$89.787	$89.79	$89.80	$89.80
Purchase #5	$189.45	12.744%	$213.5935	$213.59	$213.60	$213.60
Purchase #6	$242.76	11.756%	$271.2989	$271.30	$271.30	$271.30
Purchase #7	$235.83	9.862%	$259.0876	$259.09	$259.10	$259.10
7 purchase totals =	$939.66		$1,035.9169	$1,035.92	$1,035.95	$1,035.90