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	$173.32	9.524%	$189.827	$189.83	$189.85	$189.80
Purchase #2	$12.96	6.502%	$13.8027	$13.80	$13.80	$13.80
Purchase #3	$126.35	3.338%	$130.5676	$130.57	$130.55	$130.60
Purchase #4	$90.40	11.557%	$100.8475	$100.85	$100.85	$100.80
Purchase #5	$170.87	12.412%	$192.0784	$192.08	$192.10	$192.10
Purchase #6	$172.76	7.116%	$185.0536	$185.05	$185.05	$185.10
Purchase #7	$53.63	11.254%	$59.6655	$59.67	$59.65	$59.70
7 purchase totals =	$800.29		$871.8423	$871.85	$871.85	$871.90