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	$45.27	9.561%	$49.5983	$49.60	$49.60	$49.60
Purchase #2	$47.44	9.470%	$51.9326	$51.93	$51.95	$51.90
Purchase #3	$174.84	12.582%	$196.8384	$196.84	$196.85	$196.80
Purchase #4	$183.32	4.446%	$191.4704	$191.47	$191.45	$191.50
Purchase #5	$247.29	7.257%	$265.2358	$265.24	$265.25	$265.20
Purchase #6	$199.76	10.476%	$220.6869	$220.69	$220.70	$220.70
Purchase #7	$66.92	8.736%	$72.7661	$72.77	$72.75	$72.80
7 purchase totals =	$964.84		$1,048.5285	$1,048.54	$1,048.55	$1,048.50