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	$78.29	4.254%	$81.6205	$81.62	$81.60	$81.60
Purchase #2	$26.48	5.169%	$27.8488	$27.85	$27.85	$27.80
Purchase #3	$11.27	11.155%	$12.5272	$12.53	$12.55	$12.50
Purchase #4	$18.93	7.470%	$20.3441	$20.34	$20.35	$20.30
Purchase #5	$165.52	5.737%	$175.0159	$175.02	$175.00	$175.00
Purchase #6	$187.77	4.630%	$196.4638	$196.46	$196.45	$196.50
Purchase #7	$6.65	5.376%	$7.0075	$7.01	$7.00	$7.00
7 purchase totals =	$494.91		$520.8278	$520.83	$520.80	$520.70