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	$172.63	7.322%	$185.27	$185.27	$185.25	$185.30
Purchase #2	$214.86	3.461%	$222.2963	$222.30	$222.30	$222.30
Purchase #3	$90.84	12.443%	$102.1432	$102.14	$102.15	$102.10
Purchase #4	$98.46	11.455%	$109.7386	$109.74	$109.75	$109.70
Purchase #5	$40.61	12.108%	$45.5271	$45.53	$45.55	$45.50
Purchase #6	$81.81	4.457%	$85.4563	$85.46	$85.45	$85.50
Purchase #7	$190.35	3.219%	$196.4774	$196.48	$196.50	$196.50
7 purchase totals =	$889.56		$946.9089	$946.92	$946.95	$946.90