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	$62.47	4.439%	$65.243	$65.24	$65.25	$65.20
Purchase #2	$82.57	7.840%	$89.0435	$89.04	$89.05	$89.00
Purchase #3	$98.29	9.388%	$107.5175	$107.52	$107.50	$107.50
Purchase #4	$35.92	9.592%	$39.3654	$39.37	$39.35	$39.40
Purchase #5	$47.36	3.823%	$49.1706	$49.17	$49.15	$49.20
Purchase #6	$201.61	10.644%	$223.0694	$223.07	$223.05	$223.10
Purchase #7	$173.61	4.192%	$180.8877	$180.89	$180.90	$180.90
7 purchase totals =	$701.83		$754.2971	$754.30	$754.25	$754.30