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	$179.40	4.393%	$187.281	$187.28	$187.30	$187.30
Purchase #2	$234.59	3.867%	$243.6616	$243.66	$243.65	$243.70
Purchase #3	$50.48	10.430%	$55.7451	$55.75	$55.75	$55.70
Purchase #4	$85.79	12.503%	$96.5163	$96.52	$96.50	$96.50
Purchase #5	$83.81	7.849%	$90.3882	$90.39	$90.40	$90.40
Purchase #6	$61.27	8.562%	$66.5159	$66.52	$66.50	$66.50
Purchase #7	$213.45	4.417%	$222.8781	$222.88	$222.90	$222.90
7 purchase totals =	$908.79		$962.9862	$963.00	$963.00	$963.00