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	$85.37	7.315%	$91.6148	$91.61	$91.60	$91.60
Purchase #2	$26.65	10.351%	$29.4085	$29.41	$29.40	$29.40
Purchase #3	$85.84	7.448%	$92.2334	$92.23	$92.25	$92.20
Purchase #4	$65.54	6.178%	$69.5891	$69.59	$69.60	$69.60
Purchase #5	$33.50	11.157%	$37.2376	$37.24	$37.25	$37.20
Purchase #6	$186.78	4.107%	$194.4511	$194.45	$194.45	$194.50
Purchase #7	$102.86	9.422%	$112.5515	$112.55	$112.55	$112.60
7 purchase totals =	$586.54		$627.0860	$627.08	$627.10	$627.10