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	$147.79	13.511%	$167.7579	$167.76	$167.75	$167.80
Purchase #2	$127.77	5.490%	$134.7846	$134.78	$134.80	$134.80
Purchase #3	$188.74	6.427%	$200.8703	$200.87	$200.85	$200.90
Purchase #4	$176.32	9.405%	$192.9029	$192.90	$192.90	$192.90
Purchase #5	$30.62	4.152%	$31.8913	$31.89	$31.90	$31.90
Purchase #6	$140.52	8.545%	$152.5274	$152.53	$152.55	$152.50
Purchase #7	$141.51	5.831%	$149.7614	$149.76	$149.75	$149.80
7 purchase totals =	$953.27		$1,030.4958	$1,030.49	$1,030.50	$1,030.60