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	$151.30	8.555%	$164.2437	$164.24	$164.25	$164.20
Purchase #2	$45.39	11.701%	$50.7011	$50.70	$50.70	$50.70
Purchase #3	$161.42	6.847%	$172.4724	$172.47	$172.45	$172.50
Purchase #4	$51.56	12.266%	$57.8843	$57.88	$57.90	$57.90
Purchase #5	$37.77	7.542%	$40.6186	$40.62	$40.60	$40.60
Purchase #6	$109.99	3.718%	$114.0794	$114.08	$114.10	$114.10
Purchase #7	$213.89	9.682%	$234.5988	$234.60	$234.60	$234.60
7 purchase totals =	$771.32		$834.5983	$834.59	$834.60	$834.60