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	$195.99	8.695%	$213.0313	$213.03	$213.05	$213.00
Purchase #2	$80.43	11.781%	$89.9055	$89.91	$89.90	$89.90
Purchase #3	$101.85	3.732%	$105.651	$105.65	$105.65	$105.70
Purchase #4	$71.91	11.162%	$79.9366	$79.94	$79.95	$79.90
Purchase #5	$199.27	11.166%	$221.5205	$221.52	$221.50	$221.50
Purchase #6	$167.64	11.740%	$187.3209	$187.32	$187.30	$187.30
Purchase #7	$59.65	5.704%	$63.0524	$63.05	$63.05	$63.10
7 purchase totals =	$876.74		$960.4182	$960.42	$960.40	$960.40