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	$66.69	9.570%	$73.0722	$73.07	$73.05	$73.10
Purchase #2	$188.82	4.243%	$196.8316	$196.83	$196.85	$196.80
Purchase #3	$30.99	8.540%	$33.6365	$33.64	$33.65	$33.60
Purchase #4	$146.85	13.741%	$167.0287	$167.03	$167.05	$167.00
Purchase #5	$78.52	5.793%	$83.0687	$83.07	$83.05	$83.10
Purchase #6	$14.81	5.685%	$15.6519	$15.65	$15.65	$15.70
Purchase #7	$98.81	8.116%	$106.8294	$106.83	$106.85	$106.80
7 purchase totals =	$625.49		$676.1190	$676.12	$676.15	$676.10