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	$226.43	5.454%	$238.7795	$238.78	$238.80	$238.80
Purchase #2	$250.38	3.139%	$258.2394	$258.24	$258.25	$258.20
Purchase #3	$131.32	8.428%	$142.3876	$142.39	$142.40	$142.40
Purchase #4	$210.73	8.498%	$228.6378	$228.64	$228.65	$228.60
Purchase #5	$130.33	6.458%	$138.7467	$138.75	$138.75	$138.70
Purchase #6	$115.41	10.643%	$127.6931	$127.69	$127.70	$127.70
Purchase #7	$67.25	7.856%	$72.5332	$72.53	$72.55	$72.50
7 purchase totals =	$1,131.85		$1,207.0173	$1,207.02	$1,207.10	$1,206.90