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	$144.43	5.828%	$152.8474	$152.85	$152.85	$152.80
Purchase #2	$71.73	6.304%	$76.2519	$76.25	$76.25	$76.30
Purchase #3	$31.85	10.238%	$35.1108	$35.11	$35.10	$35.10
Purchase #4	$136.88	5.381%	$144.2455	$144.25	$144.25	$144.20
Purchase #5	$148.53	3.592%	$153.8652	$153.87	$153.85	$153.90
Purchase #6	$106.52	6.858%	$113.8251	$113.83	$113.85	$113.80
Purchase #7	$5.36	11.143%	$5.9573	$5.96	$5.95	$6.00
7 purchase totals =	$645.30		$682.1032	$682.12	$682.10	$682.10