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	$153.37	12.236%	$172.1364	$172.14	$172.15	$172.10
Purchase #2	$250.66	13.792%	$285.231	$285.23	$285.25	$285.20
Purchase #3	$173.74	8.711%	$188.8745	$188.87	$188.85	$188.90
Purchase #4	$118.86	4.222%	$123.8783	$123.88	$123.90	$123.90
Purchase #5	$154.41	3.131%	$159.2446	$159.24	$159.25	$159.20
Purchase #6	$57.69	5.665%	$60.9581	$60.96	$60.95	$61.00
Purchase #7	$78.85	7.828%	$85.0224	$85.02	$85.00	$85.00
7 purchase totals =	$987.58		$1,075.3453	$1,075.34	$1,075.35	$1,075.30