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	$176.92	8.205%	$191.4363	$191.44	$191.45	$191.40
Purchase #2	$190.54	13.263%	$215.8113	$215.81	$215.80	$215.80
Purchase #3	$81.37	13.655%	$92.4811	$92.48	$92.50	$92.50
Purchase #4	$105.59	8.331%	$114.3867	$114.39	$114.40	$114.40
Purchase #5	$173.45	5.846%	$183.5899	$183.59	$183.60	$183.60
Purchase #6	$86.48	5.552%	$91.2814	$91.28	$91.30	$91.30
Purchase #7	$242.69	10.376%	$267.8715	$267.87	$267.85	$267.90
7 purchase totals =	$1,057.04		$1,156.8582	$1,156.86	$1,156.90	$1,156.90