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	$76.35	11.851%	$85.3982	$85.40	$85.40	$85.40
Purchase #2	$162.98	3.476%	$168.6452	$168.65	$168.65	$168.60
Purchase #3	$207.86	13.550%	$236.025	$236.03	$236.05	$236.00
Purchase #4	$95.95	4.400%	$100.1718	$100.17	$100.15	$100.20
Purchase #5	$219.52	9.549%	$240.482	$240.48	$240.50	$240.50
Purchase #6	$100.62	12.835%	$113.5346	$113.53	$113.55	$113.50
Purchase #7	$40.67	5.230%	$42.797	$42.80	$42.80	$42.80
7 purchase totals =	$903.95		$987.0538	$987.06	$987.10	$987.00