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	$59.87	3.364%	$61.884	$61.88	$61.90	$61.90
Purchase #2	$20.80	4.162%	$21.6657	$21.67	$21.65	$21.70
Purchase #3	$118.54	10.568%	$131.0673	$131.07	$131.05	$131.10
Purchase #4	$192.79	9.400%	$210.9123	$210.91	$210.90	$210.90
Purchase #5	$129.94	11.483%	$144.861	$144.86	$144.85	$144.90
Purchase #6	$91.44	6.467%	$97.3534	$97.35	$97.35	$97.40
Purchase #7	$24.51	4.812%	$25.6894	$25.69	$25.70	$25.70
7 purchase totals =	$637.89		$693.4331	$693.43	$693.40	$693.60