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	$166.62	3.465%	$172.3934	$172.39	$172.40	$172.40
Purchase #2	$67.30	7.361%	$72.254	$72.25	$72.25	$72.30
Purchase #3	$32.78	9.709%	$35.9626	$35.96	$35.95	$36.00
Purchase #4	$160.38	7.732%	$172.7806	$172.78	$172.80	$172.80
Purchase #5	$110.55	3.323%	$114.2236	$114.22	$114.20	$114.20
Purchase #6	$151.68	9.210%	$165.6497	$165.65	$165.65	$165.60
Purchase #7	$177.62	3.547%	$183.9202	$183.92	$183.90	$183.90
7 purchase totals =	$866.93		$917.1841	$917.17	$917.15	$917.20