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	$78.29	9.478%	$85.7103	$85.71	$85.70	$85.70
Purchase #2	$228.85	11.736%	$255.7078	$255.71	$255.70	$255.70
Purchase #3	$12.46	5.697%	$13.1698	$13.17	$13.15	$13.20
Purchase #4	$214.90	3.563%	$222.5569	$222.56	$222.55	$222.60
Purchase #5	$8.62	9.410%	$9.4311	$9.43	$9.45	$9.40
Purchase #6	$162.44	13.374%	$184.1647	$184.16	$184.15	$184.20
Purchase #7	$75.74	6.394%	$80.5828	$80.58	$80.60	$80.60
7 purchase totals =	$781.30		$851.3234	$851.32	$851.30	$851.40