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	$85.38	12.367%	$95.9389	$95.94	$95.95	$95.90
Purchase #2	$199.87	6.795%	$213.4512	$213.45	$213.45	$213.50
Purchase #3	$107.55	3.328%	$111.1293	$111.13	$111.15	$111.10
Purchase #4	$94.31	5.616%	$99.6064	$99.61	$99.60	$99.60
Purchase #5	$186.95	10.444%	$206.4751	$206.48	$206.50	$206.50
Purchase #6	$96.63	9.714%	$106.0166	$106.02	$106.00	$106.00
Purchase #7	$141.97	9.537%	$155.5097	$155.51	$155.50	$155.50
7 purchase totals =	$912.66		$988.1272	$988.14	$988.15	$988.10