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	$88.64	10.418%	$97.8745	$97.87	$97.85	$97.90
Purchase #2	$187.28	11.634%	$209.0682	$209.07	$209.05	$209.10
Purchase #3	$64.61	4.422%	$67.4671	$67.47	$67.45	$67.50
Purchase #4	$65.96	10.336%	$72.7776	$72.78	$72.80	$72.80
Purchase #5	$23.49	10.271%	$25.9027	$25.90	$25.90	$25.90
Purchase #6	$53.75	11.713%	$60.0457	$60.05	$60.05	$60.00
Purchase #7	$36.33	5.371%	$38.2813	$38.28	$38.30	$38.30
7 purchase totals =	$520.06		$571.4171	$571.42	$571.40	$571.50