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	$225.29	3.769%	$233.7812	$233.78	$233.80	$233.80
Purchase #2	$167.85	3.563%	$173.8305	$173.83	$173.85	$173.80
Purchase #3	$248.50	8.787%	$270.3357	$270.34	$270.35	$270.30
Purchase #4	$177.67	7.493%	$190.9828	$190.98	$191.00	$191.00
Purchase #5	$94.63	5.311%	$99.6558	$99.66	$99.65	$99.70
Purchase #6	$37.62	12.496%	$42.321	$42.32	$42.30	$42.30
Purchase #7	$33.57	12.315%	$37.7041	$37.70	$37.70	$37.70
7 purchase totals =	$985.13		$1,048.6111	$1,048.61	$1,048.65	$1,048.60