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	$164.92	4.177%	$171.8087	$171.81	$171.80	$171.80
Purchase #2	$197.43	3.642%	$204.6204	$204.62	$204.60	$204.60
Purchase #3	$130.50	6.507%	$138.9916	$138.99	$139.00	$139.00
Purchase #4	$5.44	5.819%	$5.7566	$5.76	$5.75	$5.80
Purchase #5	$230.32	13.690%	$261.8508	$261.85	$261.85	$261.90
Purchase #6	$247.77	11.356%	$275.9068	$275.91	$275.90	$275.90
Purchase #7	$65.26	11.275%	$72.6181	$72.62	$72.60	$72.60
7 purchase totals =	$1,041.64		$1,131.5530	$1,131.56	$1,131.50	$1,131.60