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	$101.90	11.755%	$113.8783	$113.88	$113.90	$113.90
Purchase #2	$228.49	11.812%	$255.4792	$255.48	$255.50	$255.50
Purchase #3	$188.69	11.680%	$210.729	$210.73	$210.75	$210.70
Purchase #4	$70.71	6.141%	$75.0523	$75.05	$75.05	$75.10
Purchase #5	$143.61	5.255%	$151.1567	$151.16	$151.15	$151.20
Purchase #6	$217.91	4.114%	$226.8748	$226.87	$226.85	$226.90
Purchase #7	$37.34	12.432%	$41.9821	$41.98	$42.00	$42.00
7 purchase totals =	$988.65		$1,075.1524	$1,075.15	$1,075.20	$1,075.30