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	$155.30	4.786%	$162.7327	$162.73	$162.75	$162.70
Purchase #2	$43.40	6.655%	$46.2883	$46.29	$46.30	$46.30
Purchase #3	$58.74	11.807%	$65.6754	$65.68	$65.70	$65.70
Purchase #4	$154.50	11.575%	$172.3834	$172.38	$172.40	$172.40
Purchase #5	$168.60	11.267%	$187.5962	$187.60	$187.60	$187.60
Purchase #6	$16.37	12.162%	$18.3609	$18.36	$18.35	$18.40
Purchase #7	$49.73	8.219%	$53.8173	$53.82	$53.80	$53.80
7 purchase totals =	$646.64		$706.8542	$706.86	$706.90	$706.90