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	$76.55	11.823%	$85.6005	$85.60	$85.60	$85.60
Purchase #2	$33.83	9.630%	$37.0878	$37.09	$37.10	$37.10
Purchase #3	$215.42	6.140%	$228.6468	$228.65	$228.65	$228.60
Purchase #4	$134.91	3.525%	$139.6656	$139.67	$139.65	$139.70
Purchase #5	$48.57	9.855%	$53.3566	$53.36	$53.35	$53.40
Purchase #6	$199.59	3.809%	$207.1924	$207.19	$207.20	$207.20
Purchase #7	$35.74	13.228%	$40.4677	$40.47	$40.45	$40.50
7 purchase totals =	$744.61		$792.0174	$792.03	$792.00	$792.10