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	$104.45	4.659%	$109.3163	$109.32	$109.30	$109.30
Purchase #2	$65.88	10.511%	$72.8046	$72.80	$72.80	$72.80
Purchase #3	$43.75	4.300%	$45.6313	$45.63	$45.65	$45.60
Purchase #4	$158.86	10.690%	$175.8421	$175.84	$175.85	$175.80
Purchase #5	$43.26	7.467%	$46.4902	$46.49	$46.50	$46.50
Purchase #6	$115.71	11.327%	$128.8165	$128.82	$128.80	$128.80
Purchase #7	$32.69	9.170%	$35.6877	$35.69	$35.70	$35.70
7 purchase totals =	$564.60		$614.5887	$614.59	$614.60	$614.50