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	$47.78	9.385%	$52.2642	$52.26	$52.25	$52.30
Purchase #2	$81.93	12.635%	$92.2819	$92.28	$92.30	$92.30
Purchase #3	$124.46	5.466%	$131.263	$131.26	$131.25	$131.30
Purchase #4	$169.31	8.652%	$183.9587	$183.96	$183.95	$184.00
Purchase #5	$134.72	11.502%	$150.2155	$150.22	$150.20	$150.20
Purchase #6	$68.49	11.453%	$76.3342	$76.33	$76.35	$76.30
Purchase #7	$106.64	4.343%	$111.2714	$111.27	$111.25	$111.30
7 purchase totals =	$733.33		$797.5889	$797.58	$797.55	$797.70