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	$54.76	11.703%	$61.1686	$61.17	$61.15	$61.20
Purchase #2	$63.29	12.492%	$71.1962	$71.20	$71.20	$71.20
Purchase #3	$64.73	10.539%	$71.5519	$71.55	$71.55	$71.60
Purchase #4	$71.66	12.387%	$80.5365	$80.54	$80.55	$80.50
Purchase #5	$101.76	12.347%	$114.3243	$114.32	$114.30	$114.30
Purchase #6	$136.54	9.777%	$149.8895	$149.89	$149.90	$149.90
Purchase #7	$215.68	12.827%	$243.3453	$243.35	$243.35	$243.30
7 purchase totals =	$708.42		$792.0123	$792.02	$792.00	$792.00