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	$10.31	5.299%	$10.8563	$10.86	$10.85	$10.90
Purchase #2	$182.26	4.445%	$190.3615	$190.36	$190.35	$190.40
Purchase #3	$169.83	6.132%	$180.244	$180.24	$180.25	$180.20
Purchase #4	$106.88	11.495%	$119.1659	$119.17	$119.15	$119.20
Purchase #5	$189.78	11.105%	$210.8551	$210.86	$210.85	$210.90
Purchase #6	$101.59	4.461%	$106.1219	$106.12	$106.10	$106.10
Purchase #7	$179.25	11.412%	$199.706	$199.71	$199.70	$199.70
7 purchase totals =	$939.90		$1,017.3107	$1,017.32	$1,017.25	$1,017.40