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	$117.77	11.526%	$131.3442	$131.34	$131.35	$131.30
Purchase #2	$234.76	5.844%	$248.4794	$248.48	$248.50	$248.50
Purchase #3	$158.76	8.204%	$171.7847	$171.78	$171.80	$171.80
Purchase #4	$98.98	10.779%	$109.6491	$109.65	$109.65	$109.60
Purchase #5	$166.88	11.397%	$185.8993	$185.90	$185.90	$185.90
Purchase #6	$206.59	4.589%	$216.0704	$216.07	$216.05	$216.10
Purchase #7	$43.61	9.654%	$47.8201	$47.82	$47.80	$47.80
7 purchase totals =	$1,027.35		$1,111.0472	$1,111.04	$1,111.05	$1,111.00