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	$131.61	12.395%	$147.9231	$147.92	$147.90	$147.90
Purchase #2	$248.87	12.285%	$279.4437	$279.44	$279.45	$279.40
Purchase #3	$80.53	5.570%	$85.0155	$85.02	$85.00	$85.00
Purchase #4	$206.77	9.203%	$225.799	$225.80	$225.80	$225.80
Purchase #5	$97.82	7.128%	$104.7926	$104.79	$104.80	$104.80
Purchase #6	$188.60	4.402%	$196.9022	$196.90	$196.90	$196.90
Purchase #7	$213.66	4.603%	$223.4948	$223.49	$223.50	$223.50
7 purchase totals =	$1,167.86		$1,263.3709	$1,263.36	$1,263.35	$1,263.30