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	$79.40	12.469%	$89.3004	$89.30	$89.30	$89.30
Purchase #2	$95.27	5.526%	$100.5346	$100.53	$100.55	$100.50
Purchase #3	$121.32	5.218%	$127.6505	$127.65	$127.65	$127.70
Purchase #4	$170.91	13.443%	$193.8854	$193.89	$193.90	$193.90
Purchase #5	$91.92	4.228%	$95.8064	$95.81	$95.80	$95.80
Purchase #6	$170.60	5.452%	$179.9011	$179.90	$179.90	$179.90
Purchase #7	$90.97	9.227%	$99.3638	$99.36	$99.35	$99.40
7 purchase totals =	$820.39		$886.4422	$886.44	$886.45	$886.50