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	$90.56	11.335%	$100.825	$100.83	$100.85	$100.80
Purchase #2	$9.87	3.698%	$10.235	$10.24	$10.25	$10.20
Purchase #3	$47.98	13.161%	$54.2946	$54.29	$54.30	$54.30
Purchase #4	$75.55	6.257%	$80.2772	$80.28	$80.30	$80.30
Purchase #5	$58.99	9.130%	$64.3758	$64.38	$64.40	$64.40
Purchase #6	$237.69	13.598%	$270.0111	$270.01	$270.00	$270.00
Purchase #7	$75.81	3.314%	$78.3223	$78.32	$78.30	$78.30
7 purchase totals =	$596.45		$658.3410	$658.35	$658.40	$658.30