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	$56.63	9.268%	$61.8785	$61.88	$61.90	$61.90
Purchase #2	$80.50	11.410%	$89.6851	$89.69	$89.70	$89.70
Purchase #3	$146.27	10.553%	$161.7059	$161.71	$161.70	$161.70
Purchase #4	$229.72	8.437%	$249.1015	$249.10	$249.10	$249.10
Purchase #5	$167.50	13.119%	$189.4743	$189.47	$189.45	$189.50
Purchase #6	$69.89	9.627%	$76.6183	$76.62	$76.60	$76.60
Purchase #7	$223.99	6.269%	$238.0319	$238.03	$238.05	$238.00
7 purchase totals =	$974.50		$1,066.4955	$1,066.50	$1,066.50	$1,066.50