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	$95.88	7.351%	$102.9281	$102.93	$102.95	$102.90
Purchase #2	$90.43	13.481%	$102.6209	$102.62	$102.60	$102.60
Purchase #3	$67.26	4.537%	$70.3116	$70.31	$70.30	$70.30
Purchase #4	$166.78	13.604%	$189.4688	$189.47	$189.45	$189.50
Purchase #5	$62.96	13.861%	$71.6869	$71.69	$71.70	$71.70
Purchase #6	$77.56	7.661%	$83.5019	$83.50	$83.50	$83.50
Purchase #7	$102.86	6.811%	$109.8658	$109.87	$109.85	$109.90
7 purchase totals =	$663.73		$730.3840	$730.39	$730.35	$730.40