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	$109.71	4.287%	$114.4133	$114.41	$114.40	$114.40
Purchase #2	$43.85	10.754%	$48.5656	$48.57	$48.55	$48.60
Purchase #3	$73.84	12.578%	$83.1276	$83.13	$83.15	$83.10
Purchase #4	$104.68	12.386%	$117.6457	$117.65	$117.65	$117.60
Purchase #5	$80.74	6.557%	$86.0341	$86.03	$86.05	$86.00
Purchase #6	$219.89	13.758%	$250.1425	$250.14	$250.15	$250.10
Purchase #7	$63.88	4.301%	$66.6275	$66.63	$66.65	$66.60
7 purchase totals =	$696.59		$766.5563	$766.56	$766.60	$766.40