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	$50.86	8.557%	$55.2121	$55.21	$55.20	$55.20
Purchase #2	$17.74	13.429%	$20.1223	$20.12	$20.10	$20.10
Purchase #3	$80.87	4.439%	$84.4598	$84.46	$84.45	$84.50
Purchase #4	$55.58	4.158%	$57.891	$57.89	$57.90	$57.90
Purchase #5	$85.48	4.861%	$89.6352	$89.64	$89.65	$89.60
Purchase #6	$197.36	8.800%	$214.7277	$214.73	$214.75	$214.70
Purchase #7	$215.87	3.270%	$222.9289	$222.93	$222.95	$222.90
7 purchase totals =	$703.76		$744.9770	$744.98	$745.00	$744.90