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	$250.45	5.520%	$264.2748	$264.27	$264.25	$264.30
Purchase #2	$137.92	10.553%	$152.4747	$152.47	$152.45	$152.50
Purchase #3	$100.81	4.563%	$105.41	$105.41	$105.40	$105.40
Purchase #4	$135.48	11.147%	$150.582	$150.58	$150.60	$150.60
Purchase #5	$22.63	6.630%	$24.1304	$24.13	$24.15	$24.10
Purchase #6	$120.95	5.257%	$127.3083	$127.31	$127.30	$127.30
Purchase #7	$205.63	9.326%	$224.8071	$224.81	$224.80	$224.80
7 purchase totals =	$973.87		$1,048.9873	$1,048.98	$1,048.95	$1,049.00