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	$121.27	11.155%	$134.7977	$134.80	$134.80	$134.80
Purchase #2	$103.29	10.737%	$114.3802	$114.38	$114.40	$114.40
Purchase #3	$105.78	11.327%	$117.7617	$117.76	$117.75	$117.80
Purchase #4	$245.46	11.340%	$273.2952	$273.30	$273.30	$273.30
Purchase #5	$171.68	13.498%	$194.8534	$194.85	$194.85	$194.90
Purchase #6	$104.79	6.479%	$111.5793	$111.58	$111.60	$111.60
Purchase #7	$132.74	13.484%	$150.6387	$150.64	$150.65	$150.60
7 purchase totals =	$985.01		$1,097.3062	$1,097.31	$1,097.35	$1,097.40