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	$216.95	4.668%	$227.0772	$227.08	$227.10	$227.10
Purchase #2	$171.74	9.839%	$188.6375	$188.64	$188.65	$188.60
Purchase #3	$87.78	13.446%	$99.5829	$99.58	$99.60	$99.60
Purchase #4	$175.70	4.452%	$183.5222	$183.52	$183.50	$183.50
Purchase #5	$80.44	11.749%	$89.8909	$89.89	$89.90	$89.90
Purchase #6	$104.35	10.816%	$115.6365	$115.64	$115.65	$115.60
Purchase #7	$146.40	7.659%	$157.6128	$157.61	$157.60	$157.60
7 purchase totals =	$983.36		$1,061.9600	$1,061.96	$1,062.00	$1,061.90