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	$116.59	12.619%	$131.3025	$131.30	$131.30	$131.30
Purchase #2	$212.96	4.508%	$222.5602	$222.56	$222.55	$222.60
Purchase #3	$39.79	10.190%	$43.8446	$43.84	$43.85	$43.80
Purchase #4	$219.25	10.870%	$243.0825	$243.08	$243.10	$243.10
Purchase #5	$187.74	4.871%	$196.8848	$196.88	$196.90	$196.90
Purchase #6	$39.76	6.508%	$42.3476	$42.35	$42.35	$42.30
Purchase #7	$78.97	7.219%	$84.6708	$84.67	$84.65	$84.70
7 purchase totals =	$895.06		$964.6930	$964.68	$964.70	$964.70