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	$83.61	9.348%	$91.4259	$91.43	$91.45	$91.40
Purchase #2	$102.86	13.717%	$116.9693	$116.97	$116.95	$117.00
Purchase #3	$73.37	12.737%	$82.7151	$82.72	$82.70	$82.70
Purchase #4	$126.67	12.625%	$142.6621	$142.66	$142.65	$142.70
Purchase #5	$194.53	8.586%	$211.2323	$211.23	$211.25	$211.20
Purchase #6	$56.71	4.257%	$59.1241	$59.12	$59.10	$59.10
Purchase #7	$151.41	6.569%	$161.3561	$161.36	$161.35	$161.40
7 purchase totals =	$789.16		$865.4849	$865.49	$865.45	$865.50