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	$94.25	5.314%	$99.2584	$99.26	$99.25	$99.30
Purchase #2	$6.47	10.156%	$7.1271	$7.13	$7.15	$7.10
Purchase #3	$102.30	7.802%	$110.2814	$110.28	$110.30	$110.30
Purchase #4	$204.35	8.408%	$221.5317	$221.53	$221.55	$221.50
Purchase #5	$173.66	13.257%	$196.6821	$196.68	$196.70	$196.70
Purchase #6	$227.48	11.802%	$254.3272	$254.33	$254.35	$254.30
Purchase #7	$111.50	6.608%	$118.8679	$118.87	$118.85	$118.90
7 purchase totals =	$920.01		$1,008.0758	$1,008.08	$1,008.15	$1,008.10