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	$156.36	5.139%	$164.3953	$164.40	$164.40	$164.40
Purchase #2	$104.63	5.256%	$110.1294	$110.13	$110.15	$110.10
Purchase #3	$52.74	8.793%	$57.3774	$57.38	$57.40	$57.40
Purchase #4	$32.57	6.222%	$34.5965	$34.60	$34.60	$34.60
Purchase #5	$198.69	13.474%	$225.4615	$225.46	$225.45	$225.50
Purchase #6	$173.66	13.301%	$196.7585	$196.76	$196.75	$196.80
Purchase #7	$195.39	5.804%	$206.7304	$206.73	$206.75	$206.70
7 purchase totals =	$914.04		$995.4490	$995.46	$995.50	$995.50