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	$67.86	8.654%	$73.7326	$73.73	$73.75	$73.70
Purchase #2	$94.68	3.830%	$98.3062	$98.31	$98.30	$98.30
Purchase #3	$96.36	4.530%	$100.7251	$100.73	$100.75	$100.70
Purchase #4	$247.89	11.147%	$275.5223	$275.52	$275.50	$275.50
Purchase #5	$149.94	6.755%	$160.0684	$160.07	$160.05	$160.10
Purchase #6	$99.35	6.246%	$105.5554	$105.56	$105.55	$105.60
Purchase #7	$96.70	5.439%	$101.9595	$101.96	$101.95	$102.00
7 purchase totals =	$852.78		$915.8695	$915.88	$915.85	$915.90