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	$81.53	8.408%	$88.385	$88.39	$88.40	$88.40
Purchase #2	$105.85	6.206%	$112.4191	$112.42	$112.40	$112.40
Purchase #3	$82.57	12.454%	$92.8533	$92.85	$92.85	$92.90
Purchase #4	$215.92	11.755%	$241.3014	$241.30	$241.30	$241.30
Purchase #5	$114.70	7.758%	$123.5984	$123.60	$123.60	$123.60
Purchase #6	$85.49	4.687%	$89.4969	$89.50	$89.50	$89.50
Purchase #7	$192.89	7.322%	$207.0134	$207.01	$207.00	$207.00
7 purchase totals =	$878.95		$955.0675	$955.07	$955.05	$955.10