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	$137.90	8.294%	$149.3374	$149.34	$149.35	$149.30
Purchase #2	$185.50	6.157%	$196.9212	$196.92	$196.90	$196.90
Purchase #3	$233.97	9.371%	$255.8953	$255.90	$255.90	$255.90
Purchase #4	$176.82	3.820%	$183.5745	$183.57	$183.55	$183.60
Purchase #5	$238.52	6.740%	$254.5962	$254.60	$254.60	$254.60
Purchase #6	$167.67	4.361%	$174.9821	$174.98	$175.00	$175.00
Purchase #7	$244.41	11.226%	$271.8475	$271.85	$271.85	$271.80
7 purchase totals =	$1,384.79		$1,487.1542	$1,487.16	$1,487.15	$1,487.10