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	$208.60	10.311%	$230.1087	$230.11	$230.10	$230.10
Purchase #2	$184.99	11.664%	$206.5672	$206.57	$206.55	$206.60
Purchase #3	$65.36	3.250%	$67.4842	$67.48	$67.50	$67.50
Purchase #4	$69.79	12.500%	$78.5138	$78.51	$78.50	$78.50
Purchase #5	$16.97	9.253%	$18.5402	$18.54	$18.55	$18.50
Purchase #6	$30.98	9.436%	$33.9033	$33.90	$33.90	$33.90
Purchase #7	$155.91	12.453%	$175.3255	$175.33	$175.35	$175.30
7 purchase totals =	$732.60		$810.4429	$810.44	$810.45	$810.40