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	$166.94	11.395%	$185.9628	$185.96	$185.95	$186.00
Purchase #2	$191.50	3.625%	$198.4419	$198.44	$198.45	$198.40
Purchase #3	$154.42	6.505%	$164.465	$164.47	$164.45	$164.50
Purchase #4	$10.62	11.276%	$11.8175	$11.82	$11.80	$11.80
Purchase #5	$144.77	3.721%	$150.1569	$150.16	$150.15	$150.20
Purchase #6	$107.76	3.860%	$111.9195	$111.92	$111.90	$111.90
Purchase #7	$246.28	11.261%	$274.0136	$274.01	$274.00	$274.00
7 purchase totals =	$1,022.29		$1,096.7772	$1,096.78	$1,096.70	$1,096.80