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	$135.41	9.589%	$148.3945	$148.39	$148.40	$148.40
Purchase #2	$48.35	4.108%	$50.3362	$50.34	$50.35	$50.30
Purchase #3	$121.90	7.553%	$131.1071	$131.11	$131.10	$131.10
Purchase #4	$205.82	6.109%	$218.3935	$218.39	$218.40	$218.40
Purchase #5	$138.52	8.676%	$150.538	$150.54	$150.55	$150.50
Purchase #6	$137.83	3.498%	$142.6513	$142.65	$142.65	$142.70
Purchase #7	$250.76	4.336%	$261.633	$261.63	$261.65	$261.60
7 purchase totals =	$1,038.59		$1,103.0536	$1,103.05	$1,103.10	$1,103.00