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	$85.27	10.295%	$94.0485	$94.05	$94.05	$94.00
Purchase #2	$95.87	10.856%	$106.2776	$106.28	$106.30	$106.30
Purchase #3	$162.38	3.560%	$168.1607	$168.16	$168.15	$168.20
Purchase #4	$240.32	6.143%	$255.0829	$255.08	$255.10	$255.10
Purchase #5	$7.48	6.146%	$7.9397	$7.94	$7.95	$7.90
Purchase #6	$161.79	7.179%	$173.4049	$173.40	$173.40	$173.40
Purchase #7	$65.58	10.201%	$72.2698	$72.27	$72.25	$72.30
7 purchase totals =	$818.69		$877.1841	$877.18	$877.20	$877.20