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	$153.88	9.492%	$168.4863	$168.49	$168.50	$168.50
Purchase #2	$126.52	11.790%	$141.4367	$141.44	$141.45	$141.40
Purchase #3	$108.92	8.600%	$118.2871	$118.29	$118.30	$118.30
Purchase #4	$16.92	3.136%	$17.4506	$17.45	$17.45	$17.50
Purchase #5	$227.32	10.477%	$251.1363	$251.14	$251.15	$251.10
Purchase #6	$79.56	3.525%	$82.3645	$82.36	$82.35	$82.40
Purchase #7	$217.89	11.319%	$242.553	$242.55	$242.55	$242.60
7 purchase totals =	$931.01		$1,021.7145	$1,021.72	$1,021.75	$1,021.80