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	$87.30	9.434%	$95.5359	$95.54	$95.55	$95.50
Purchase #2	$67.74	5.450%	$71.4318	$71.43	$71.45	$71.40
Purchase #3	$47.29	4.713%	$49.5188	$49.52	$49.50	$49.50
Purchase #4	$179.32	11.194%	$199.3931	$199.39	$199.40	$199.40
Purchase #5	$42.97	6.570%	$45.7931	$45.79	$45.80	$45.80
Purchase #6	$123.69	7.786%	$133.3205	$133.32	$133.30	$133.30
Purchase #7	$77.34	5.557%	$81.6378	$81.64	$81.65	$81.60
7 purchase totals =	$625.65		$676.6310	$676.63	$676.65	$676.50