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	$109.72	12.860%	$123.83	$123.83	$123.85	$123.80
Purchase #2	$14.43	8.276%	$15.6242	$15.62	$15.60	$15.60
Purchase #3	$79.88	3.381%	$82.5807	$82.58	$82.60	$82.60
Purchase #4	$248.76	4.749%	$260.5736	$260.57	$260.55	$260.60
Purchase #5	$54.73	3.441%	$56.6133	$56.61	$56.60	$56.60
Purchase #6	$39.43	5.345%	$41.5375	$41.54	$41.55	$41.50
Purchase #7	$165.36	6.221%	$175.647	$175.65	$175.65	$175.60
7 purchase totals =	$712.31		$756.4063	$756.40	$756.40	$756.30