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	$226.51	8.191%	$245.0634	$245.06	$245.05	$245.10
Purchase #2	$58.63	10.539%	$64.809	$64.81	$64.80	$64.80
Purchase #3	$103.41	8.553%	$112.2547	$112.25	$112.25	$112.30
Purchase #4	$235.94	11.240%	$262.4597	$262.46	$262.45	$262.50
Purchase #5	$171.51	8.334%	$185.8036	$185.80	$185.80	$185.80
Purchase #6	$52.65	13.644%	$59.8336	$59.83	$59.85	$59.80
Purchase #7	$45.63	12.406%	$51.2909	$51.29	$51.30	$51.30
7 purchase totals =	$894.28		$981.5149	$981.50	$981.50	$981.60