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	$124.87	5.501%	$131.7391	$131.74	$131.75	$131.70
Purchase #2	$16.29	4.871%	$17.0835	$17.08	$17.10	$17.10
Purchase #3	$95.69	7.556%	$102.9203	$102.92	$102.90	$102.90
Purchase #4	$82.87	11.520%	$92.4166	$92.42	$92.40	$92.40
Purchase #5	$209.54	7.136%	$224.4928	$224.49	$224.50	$224.50
Purchase #6	$104.69	6.548%	$111.5451	$111.55	$111.55	$111.50
Purchase #7	$29.84	4.376%	$31.1458	$31.15	$31.15	$31.10
7 purchase totals =	$663.79		$711.3432	$711.35	$711.35	$711.20