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	$214.89	5.211%	$226.0879	$226.09	$226.10	$226.10
Purchase #2	$148.74	6.420%	$158.2891	$158.29	$158.30	$158.30
Purchase #3	$47.66	11.459%	$53.1214	$53.12	$53.10	$53.10
Purchase #4	$219.25	4.854%	$229.8924	$229.89	$229.90	$229.90
Purchase #5	$245.69	3.450%	$254.1663	$254.17	$254.15	$254.20
Purchase #6	$7.36	13.676%	$8.3666	$8.37	$8.35	$8.40
Purchase #7	$66.78	8.797%	$72.6546	$72.65	$72.65	$72.70
7 purchase totals =	$950.37		$1,002.5783	$1,002.58	$1,002.55	$1,002.70