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	$42.27	7.787%	$45.5616	$45.56	$45.55	$45.60
Purchase #2	$56.80	7.294%	$60.943	$60.94	$60.95	$60.90
Purchase #3	$42.66	6.242%	$45.3228	$45.32	$45.30	$45.30
Purchase #4	$217.55	3.378%	$224.8988	$224.90	$224.90	$224.90
Purchase #5	$32.72	7.785%	$35.2673	$35.27	$35.25	$35.30
Purchase #6	$204.57	3.669%	$212.0757	$212.08	$212.10	$212.10
Purchase #7	$67.81	4.576%	$70.913	$70.91	$70.90	$70.90
7 purchase totals =	$664.38		$694.9822	$694.98	$694.95	$695.00