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	$77.39	10.615%	$85.6049	$85.60	$85.60	$85.60
Purchase #2	$101.50	7.764%	$109.3805	$109.38	$109.40	$109.40
Purchase #3	$95.54	5.117%	$100.4288	$100.43	$100.45	$100.40
Purchase #4	$127.36	11.308%	$141.7619	$141.76	$141.75	$141.80
Purchase #5	$118.80	3.834%	$123.3548	$123.35	$123.35	$123.40
Purchase #6	$89.38	3.593%	$92.5914	$92.59	$92.60	$92.60
Purchase #7	$50.86	3.329%	$52.5531	$52.55	$52.55	$52.60
7 purchase totals =	$660.83		$705.6754	$705.66	$705.70	$705.80