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	$136.35	10.238%	$150.3095	$150.31	$150.30	$150.30
Purchase #2	$53.61	9.549%	$58.7292	$58.73	$58.75	$58.70
Purchase #3	$18.72	7.445%	$20.1137	$20.11	$20.10	$20.10
Purchase #4	$240.69	6.262%	$255.762	$255.76	$255.75	$255.80
Purchase #5	$42.67	5.287%	$44.926	$44.93	$44.95	$44.90
Purchase #6	$5.95	10.499%	$6.5747	$6.57	$6.55	$6.60
Purchase #7	$241.79	3.454%	$250.1414	$250.14	$250.15	$250.10
7 purchase totals =	$739.78		$786.5565	$786.55	$786.55	$786.50