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	$65.69	10.552%	$72.6216	$72.62	$72.60	$72.60
Purchase #2	$230.93	12.356%	$259.4637	$259.46	$259.45	$259.50
Purchase #3	$132.43	6.292%	$140.7625	$140.76	$140.75	$140.80
Purchase #4	$134.59	3.815%	$139.7246	$139.72	$139.70	$139.70
Purchase #5	$209.68	5.798%	$221.8372	$221.84	$221.85	$221.80
Purchase #6	$19.46	5.151%	$20.4624	$20.46	$20.45	$20.50
Purchase #7	$175.65	11.398%	$195.6706	$195.67	$195.65	$195.70
7 purchase totals =	$968.43		$1,050.5426	$1,050.53	$1,050.45	$1,050.60