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	$111.94	6.450%	$119.1601	$119.16	$119.15	$119.20
Purchase #2	$155.35	10.333%	$171.4023	$171.40	$171.40	$171.40
Purchase #3	$66.87	7.782%	$72.0738	$72.07	$72.05	$72.10
Purchase #4	$166.89	12.147%	$187.1621	$187.16	$187.15	$187.20
Purchase #5	$235.37	3.809%	$244.3352	$244.34	$244.35	$244.30
Purchase #6	$247.38	5.646%	$261.3471	$261.35	$261.35	$261.30
Purchase #7	$26.41	13.211%	$29.899	$29.90	$29.90	$29.90
7 purchase totals =	$1,010.21		$1,085.3796	$1,085.38	$1,085.35	$1,085.40