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	$18.47	6.196%	$19.6144	$19.61	$19.60	$19.60
Purchase #2	$34.87	12.218%	$39.1304	$39.13	$39.15	$39.10
Purchase #3	$41.99	3.858%	$43.61	$43.61	$43.60	$43.60
Purchase #4	$65.82	13.278%	$74.5596	$74.56	$74.55	$74.60
Purchase #5	$125.35	4.628%	$131.1512	$131.15	$131.15	$131.20
Purchase #6	$250.36	12.764%	$282.316	$282.32	$282.30	$282.30
Purchase #7	$28.45	5.249%	$29.9433	$29.94	$29.95	$29.90
7 purchase totals =	$565.31		$620.3249	$620.32	$620.30	$620.30