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	$92.37	13.591%	$104.924	$104.92	$104.90	$104.90
Purchase #2	$14.99	3.672%	$15.5404	$15.54	$15.55	$15.50
Purchase #3	$192.59	12.272%	$216.2246	$216.22	$216.20	$216.20
Purchase #4	$147.27	10.574%	$162.8423	$162.84	$162.85	$162.80
Purchase #5	$233.89	5.848%	$247.5679	$247.57	$247.55	$247.60
Purchase #6	$206.97	11.689%	$231.1627	$231.16	$231.15	$231.20
Purchase #7	$98.79	12.646%	$111.283	$111.28	$111.30	$111.30
7 purchase totals =	$986.87		$1,089.5449	$1,089.53	$1,089.50	$1,089.50