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	$192.98	11.814%	$215.7787	$215.78	$215.80	$215.80
Purchase #2	$40.81	10.294%	$45.011	$45.01	$45.00	$45.00
Purchase #3	$215.74	11.764%	$241.1197	$241.12	$241.10	$241.10
Purchase #4	$100.75	12.417%	$113.2601	$113.26	$113.25	$113.30
Purchase #5	$116.32	3.560%	$120.461	$120.46	$120.45	$120.50
Purchase #6	$142.67	13.191%	$161.4896	$161.49	$161.50	$161.50
Purchase #7	$174.88	8.328%	$189.444	$189.44	$189.45	$189.40
7 purchase totals =	$984.15		$1,086.5641	$1,086.56	$1,086.55	$1,086.60