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	$91.68	13.532%	$104.0861	$104.09	$104.10	$104.10
Purchase #2	$93.26	9.810%	$102.4088	$102.41	$102.40	$102.40
Purchase #3	$18.27	13.650%	$20.7639	$20.76	$20.75	$20.80
Purchase #4	$213.58	9.525%	$233.9235	$233.92	$233.90	$233.90
Purchase #5	$123.82	6.524%	$131.898	$131.90	$131.90	$131.90
Purchase #6	$50.98	4.661%	$53.3562	$53.36	$53.35	$53.40
Purchase #7	$226.82	5.206%	$238.6282	$238.63	$238.65	$238.60
7 purchase totals =	$818.41		$885.0647	$885.07	$885.05	$885.10