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	$18.64	5.568%	$19.6779	$19.68	$19.70	$19.70
Purchase #2	$58.72	5.866%	$62.1645	$62.16	$62.15	$62.20
Purchase #3	$79.57	3.737%	$82.5435	$82.54	$82.55	$82.50
Purchase #4	$172.89	10.147%	$190.4331	$190.43	$190.45	$190.40
Purchase #5	$28.46	13.619%	$32.336	$32.34	$32.35	$32.30
Purchase #6	$120.73	3.441%	$124.8843	$124.88	$124.90	$124.90
Purchase #7	$233.72	7.649%	$251.5972	$251.60	$251.60	$251.60
7 purchase totals =	$712.73		$763.6365	$763.63	$763.70	$763.60