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	$78.58	5.599%	$82.9797	$82.98	$83.00	$83.00
Purchase #2	$135.31	3.281%	$139.7495	$139.75	$139.75	$139.70
Purchase #3	$233.32	7.326%	$250.413	$250.41	$250.40	$250.40
Purchase #4	$82.32	7.657%	$88.6232	$88.62	$88.60	$88.60
Purchase #5	$61.44	9.857%	$67.4961	$67.50	$67.50	$67.50
Purchase #6	$198.76	10.193%	$219.0196	$219.02	$219.00	$219.00
Purchase #7	$104.68	7.252%	$112.2714	$112.27	$112.25	$112.30
7 purchase totals =	$894.41		$960.5525	$960.55	$960.50	$960.50