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	$32.77	8.136%	$35.4362	$35.44	$35.45	$35.40
Purchase #2	$184.41	6.481%	$196.3616	$196.36	$196.35	$196.40
Purchase #3	$51.89	9.430%	$56.7832	$56.78	$56.80	$56.80
Purchase #4	$32.99	13.809%	$37.5456	$37.55	$37.55	$37.50
Purchase #5	$117.39	7.281%	$125.9372	$125.94	$125.95	$125.90
Purchase #6	$225.35	9.233%	$246.1566	$246.16	$246.15	$246.20
Purchase #7	$11.33	6.265%	$12.0398	$12.04	$12.05	$12.00
7 purchase totals =	$656.13		$710.2602	$710.27	$710.30	$710.20