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	$81.25	6.639%	$86.6442	$86.64	$86.65	$86.60
Purchase #2	$75.91	4.543%	$79.3586	$79.36	$79.35	$79.40
Purchase #3	$10.96	13.769%	$12.4691	$12.47	$12.45	$12.50
Purchase #4	$10.72	3.752%	$11.1222	$11.12	$11.10	$11.10
Purchase #5	$114.31	6.597%	$121.851	$121.85	$121.85	$121.90
Purchase #6	$65.70	10.418%	$72.5446	$72.54	$72.55	$72.50
Purchase #7	$65.48	12.410%	$73.6061	$73.61	$73.60	$73.60
7 purchase totals =	$424.33		$457.5958	$457.59	$457.55	$457.60