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	$199.93	11.799%	$223.5197	$223.52	$223.50	$223.50
Purchase #2	$196.41	13.155%	$222.2477	$222.25	$222.25	$222.20
Purchase #3	$134.44	13.797%	$152.9887	$152.99	$153.00	$153.00
Purchase #4	$168.87	13.448%	$191.5796	$191.58	$191.60	$191.60
Purchase #5	$46.33	10.242%	$51.0751	$51.08	$51.10	$51.10
Purchase #6	$171.46	7.419%	$184.1806	$184.18	$184.20	$184.20
Purchase #7	$29.39	5.516%	$31.0112	$31.01	$31.00	$31.00
7 purchase totals =	$946.83		$1,056.6026	$1,056.61	$1,056.65	$1,056.60