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	$108.50	10.256%	$119.6278	$119.63	$119.65	$119.60
Purchase #2	$83.53	8.631%	$90.7395	$90.74	$90.75	$90.70
Purchase #3	$64.33	13.298%	$72.8846	$72.88	$72.90	$72.90
Purchase #4	$133.50	5.345%	$140.6356	$140.64	$140.65	$140.60
Purchase #5	$215.32	5.567%	$227.3069	$227.31	$227.30	$227.30
Purchase #6	$196.54	7.419%	$211.1213	$211.12	$211.10	$211.10
Purchase #7	$82.92	8.306%	$89.8073	$89.81	$89.80	$89.80
7 purchase totals =	$884.64		$952.1230	$952.13	$952.15	$952.00