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	$46.50	3.448%	$48.1033	$48.10	$48.10	$48.10
Purchase #2	$35.96	12.426%	$40.4284	$40.43	$40.45	$40.40
Purchase #3	$19.43	10.652%	$21.4997	$21.50	$21.50	$21.50
Purchase #4	$228.86	8.260%	$247.7638	$247.76	$247.75	$247.80
Purchase #5	$168.39	10.321%	$185.7695	$185.77	$185.75	$185.80
Purchase #6	$247.59	9.270%	$270.5416	$270.54	$270.55	$270.50
Purchase #7	$245.45	3.171%	$253.2332	$253.23	$253.25	$253.20
7 purchase totals =	$992.18		$1,067.3395	$1,067.33	$1,067.35	$1,067.30