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	$105.43	13.445%	$119.6051	$119.61	$119.60	$119.60
Purchase #2	$28.76	7.824%	$31.0102	$31.01	$31.00	$31.00
Purchase #3	$96.68	5.255%	$101.7605	$101.76	$101.75	$101.80
Purchase #4	$21.36	11.106%	$23.7322	$23.73	$23.75	$23.70
Purchase #5	$119.78	6.104%	$127.0914	$127.09	$127.10	$127.10
Purchase #6	$29.93	11.358%	$33.3294	$33.33	$33.35	$33.30
Purchase #7	$104.71	6.515%	$111.5319	$111.53	$111.55	$111.50
7 purchase totals =	$506.65		$548.0607	$548.06	$548.10	$548.00