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	$85.71	6.569%	$91.3403	$91.34	$91.35	$91.30
Purchase #2	$180.66	3.775%	$187.4799	$187.48	$187.50	$187.50
Purchase #3	$202.43	7.569%	$217.7519	$217.75	$217.75	$217.80
Purchase #4	$68.57	6.188%	$72.8131	$72.81	$72.80	$72.80
Purchase #5	$242.32	11.701%	$270.6739	$270.67	$270.65	$270.70
Purchase #6	$72.40	11.150%	$80.4726	$80.47	$80.45	$80.50
Purchase #7	$175.25	5.661%	$185.1709	$185.17	$185.15	$185.20
7 purchase totals =	$1,027.34		$1,105.7026	$1,105.69	$1,105.65	$1,105.80