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	$55.25	13.760%	$62.8524	$62.85	$62.85	$62.90
Purchase #2	$238.42	7.616%	$256.5781	$256.58	$256.60	$256.60
Purchase #3	$229.75	12.446%	$258.3447	$258.34	$258.35	$258.30
Purchase #4	$12.66	3.150%	$13.0588	$13.06	$13.05	$13.10
Purchase #5	$148.94	9.138%	$162.5501	$162.55	$162.55	$162.60
Purchase #6	$27.35	12.829%	$30.8587	$30.86	$30.85	$30.90
Purchase #7	$64.35	4.498%	$67.2445	$67.24	$67.25	$67.20
7 purchase totals =	$776.72		$851.4873	$851.48	$851.50	$851.60