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	$112.33	10.240%	$123.8326	$123.83	$123.85	$123.80
Purchase #2	$57.60	3.344%	$59.5261	$59.53	$59.55	$59.50
Purchase #3	$111.33	3.621%	$115.3613	$115.36	$115.35	$115.40
Purchase #4	$190.34	11.318%	$211.8827	$211.88	$211.90	$211.90
Purchase #5	$227.48	13.716%	$258.6812	$258.68	$258.70	$258.70
Purchase #6	$146.30	7.826%	$157.7494	$157.75	$157.75	$157.70
Purchase #7	$93.45	6.499%	$99.5233	$99.52	$99.50	$99.50
7 purchase totals =	$938.83		$1,026.5566	$1,026.55	$1,026.60	$1,026.50