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	$133.37	11.542%	$148.7636	$148.76	$148.75	$148.80
Purchase #2	$141.58	4.709%	$148.247	$148.25	$148.25	$148.20
Purchase #3	$100.93	10.615%	$111.6437	$111.64	$111.65	$111.60
Purchase #4	$190.34	12.719%	$214.5493	$214.55	$214.55	$214.50
Purchase #5	$36.78	13.670%	$41.8078	$41.81	$41.80	$41.80
Purchase #6	$96.47	13.106%	$109.1134	$109.11	$109.10	$109.10
Purchase #7	$67.28	4.308%	$70.1784	$70.18	$70.20	$70.20
7 purchase totals =	$766.75		$844.3032	$844.30	$844.30	$844.20