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	$93.44	11.759%	$104.4276	$104.43	$104.45	$104.40
Purchase #2	$131.48	5.420%	$138.6062	$138.61	$138.60	$138.60
Purchase #3	$242.88	5.450%	$256.117	$256.12	$256.10	$256.10
Purchase #4	$37.27	8.281%	$40.3563	$40.36	$40.35	$40.40
Purchase #5	$174.44	4.520%	$182.3247	$182.32	$182.30	$182.30
Purchase #6	$154.57	9.359%	$169.0362	$169.04	$169.05	$169.00
Purchase #7	$171.89	13.235%	$194.6396	$194.64	$194.65	$194.60
7 purchase totals =	$1,005.97		$1,085.5076	$1,085.52	$1,085.50	$1,085.40