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	$188.34	11.224%	$209.4793	$209.48	$209.50	$209.50
Purchase #2	$179.89	11.624%	$200.8004	$200.80	$200.80	$200.80
Purchase #3	$78.56	5.241%	$82.6773	$82.68	$82.70	$82.70
Purchase #4	$178.60	9.187%	$195.008	$195.01	$195.00	$195.00
Purchase #5	$96.95	12.156%	$108.7352	$108.74	$108.75	$108.70
Purchase #6	$41.73	6.816%	$44.5743	$44.57	$44.55	$44.60
Purchase #7	$239.86	10.177%	$264.2706	$264.27	$264.25	$264.30
7 purchase totals =	$1,003.93		$1,105.5451	$1,105.55	$1,105.55	$1,105.60