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	$199.74	4.588%	$208.9041	$208.90	$208.90	$208.90
Purchase #2	$147.97	13.676%	$168.2064	$168.21	$168.20	$168.20
Purchase #3	$9.51	10.219%	$10.4818	$10.48	$10.50	$10.50
Purchase #4	$127.94	13.735%	$145.5126	$145.51	$145.50	$145.50
Purchase #5	$178.41	5.572%	$188.351	$188.35	$188.35	$188.40
Purchase #6	$191.37	13.133%	$216.5026	$216.50	$216.50	$216.50
Purchase #7	$142.27	3.700%	$147.534	$147.53	$147.55	$147.50
7 purchase totals =	$997.21		$1,085.4925	$1,085.48	$1,085.50	$1,085.50