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	$220.84	6.628%	$235.4773	$235.48	$235.50	$235.50
Purchase #2	$208.34	5.228%	$219.232	$219.23	$219.25	$219.20
Purchase #3	$60.29	6.322%	$64.1015	$64.10	$64.10	$64.10
Purchase #4	$40.52	12.647%	$45.6446	$45.64	$45.65	$45.60
Purchase #5	$79.59	5.177%	$83.7104	$83.71	$83.70	$83.70
Purchase #6	$173.71	3.551%	$179.8784	$179.88	$179.90	$179.90
Purchase #7	$208.71	7.241%	$223.8227	$223.82	$223.80	$223.80
7 purchase totals =	$992.00		$1,051.8669	$1,051.86	$1,051.90	$1,051.80