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	$171.62	10.602%	$189.8152	$189.82	$189.80	$189.80
Purchase #2	$216.86	11.627%	$242.0743	$242.07	$242.05	$242.10
Purchase #3	$198.80	9.334%	$217.356	$217.36	$217.35	$217.40
Purchase #4	$57.41	13.822%	$65.3452	$65.35	$65.35	$65.30
Purchase #5	$39.62	6.150%	$42.0566	$42.06	$42.05	$42.10
Purchase #6	$100.91	5.552%	$106.5125	$106.51	$106.50	$106.50
Purchase #7	$222.65	12.459%	$250.39	$250.39	$250.40	$250.40
7 purchase totals =	$1,007.87		$1,113.5498	$1,113.56	$1,113.50	$1,113.60