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	$51.26	13.283%	$58.0689	$58.07	$58.05	$58.10
Purchase #2	$113.25	12.268%	$127.1435	$127.14	$127.15	$127.10
Purchase #3	$33.66	11.830%	$37.642	$37.64	$37.65	$37.60
Purchase #4	$173.97	5.753%	$183.9785	$183.98	$184.00	$184.00
Purchase #5	$47.86	13.481%	$54.312	$54.31	$54.30	$54.30
Purchase #6	$150.43	9.206%	$164.2786	$164.28	$164.30	$164.30
Purchase #7	$160.44	5.164%	$168.7251	$168.73	$168.75	$168.70
7 purchase totals =	$730.87		$794.1486	$794.15	$794.20	$794.10