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	$156.95	7.295%	$168.3995	$168.40	$168.40	$168.40
Purchase #2	$173.75	9.317%	$189.9383	$189.94	$189.95	$189.90
Purchase #3	$86.37	3.431%	$89.3334	$89.33	$89.35	$89.30
Purchase #4	$9.34	12.226%	$10.4819	$10.48	$10.50	$10.50
Purchase #5	$110.35	7.861%	$119.0246	$119.02	$119.00	$119.00
Purchase #6	$49.49	7.152%	$53.0295	$53.03	$53.05	$53.00
Purchase #7	$89.57	12.203%	$100.5002	$100.50	$100.50	$100.50
7 purchase totals =	$675.82		$730.7074	$730.70	$730.75	$730.60