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	$40.49	10.431%	$44.7135	$44.71	$44.70	$44.70
Purchase #2	$205.84	7.811%	$221.9182	$221.92	$221.90	$221.90
Purchase #3	$142.90	7.180%	$153.1602	$153.16	$153.15	$153.20
Purchase #4	$31.77	6.758%	$33.917	$33.92	$33.90	$33.90
Purchase #5	$136.67	11.320%	$152.141	$152.14	$152.15	$152.10
Purchase #6	$180.50	12.547%	$203.1473	$203.15	$203.15	$203.10
Purchase #7	$56.78	4.394%	$59.2749	$59.27	$59.25	$59.30
7 purchase totals =	$794.95		$868.2721	$868.27	$868.20	$868.20