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	$53.92	9.582%	$59.0866	$59.09	$59.10	$59.10
Purchase #2	$137.28	7.416%	$147.4607	$147.46	$147.45	$147.50
Purchase #3	$89.92	12.160%	$100.8543	$100.85	$100.85	$100.90
Purchase #4	$227.54	6.698%	$242.7806	$242.78	$242.80	$242.80
Purchase #5	$123.64	5.756%	$130.7567	$130.76	$130.75	$130.80
Purchase #6	$193.62	7.571%	$208.279	$208.28	$208.30	$208.30
Purchase #7	$215.87	4.735%	$226.0914	$226.09	$226.10	$226.10
7 purchase totals =	$1,041.79		$1,115.3093	$1,115.31	$1,115.35	$1,115.50