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	$75.98	7.546%	$81.7135	$81.71	$81.70	$81.70
Purchase #2	$23.39	9.391%	$25.5866	$25.59	$25.60	$25.60
Purchase #3	$48.62	13.312%	$55.0923	$55.09	$55.10	$55.10
Purchase #4	$41.35	10.202%	$45.5685	$45.57	$45.55	$45.60
Purchase #5	$52.46	5.483%	$55.3364	$55.34	$55.35	$55.30
Purchase #6	$165.42	7.795%	$178.3145	$178.31	$178.30	$178.30
Purchase #7	$171.67	8.167%	$185.6903	$185.69	$185.70	$185.70
7 purchase totals =	$578.89		$627.3021	$627.30	$627.30	$627.30