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	$167.76	10.615%	$185.5677	$185.57	$185.55	$185.60
Purchase #2	$140.26	9.452%	$153.5174	$153.52	$153.50	$153.50
Purchase #3	$18.51	9.857%	$20.3345	$20.33	$20.35	$20.30
Purchase #4	$242.90	9.721%	$266.5123	$266.51	$266.50	$266.50
Purchase #5	$127.99	13.507%	$145.2776	$145.28	$145.30	$145.30
Purchase #6	$56.83	11.333%	$63.2705	$63.27	$63.25	$63.30
Purchase #7	$91.30	11.209%	$101.5338	$101.53	$101.55	$101.50
7 purchase totals =	$845.55		$936.0138	$936.01	$936.00	$936.00