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	$28.77	13.329%	$32.6048	$32.60	$32.60	$32.60
Purchase #2	$10.47	8.160%	$11.3244	$11.32	$11.30	$11.30
Purchase #3	$39.78	11.243%	$44.2525	$44.25	$44.25	$44.30
Purchase #4	$164.56	9.208%	$179.7127	$179.71	$179.70	$179.70
Purchase #5	$210.46	8.823%	$229.0289	$229.03	$229.05	$229.00
Purchase #6	$106.61	3.148%	$109.9661	$109.97	$109.95	$110.00
Purchase #7	$180.89	4.260%	$188.5959	$188.60	$188.60	$188.60
7 purchase totals =	$741.54		$795.4853	$795.48	$795.45	$795.50