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	$205.35	10.407%	$226.7208	$226.72	$226.70	$226.70
Purchase #2	$39.94	9.127%	$43.5853	$43.59	$43.60	$43.60
Purchase #3	$58.43	12.349%	$65.6455	$65.65	$65.65	$65.60
Purchase #4	$84.38	9.416%	$92.3252	$92.33	$92.35	$92.30
Purchase #5	$52.51	12.825%	$59.2444	$59.24	$59.25	$59.20
Purchase #6	$42.79	6.344%	$45.5046	$45.50	$45.50	$45.50
Purchase #7	$107.48	13.430%	$121.9146	$121.91	$121.90	$121.90
7 purchase totals =	$590.88		$654.9404	$654.94	$654.95	$654.80