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	$82.43	8.279%	$89.2544	$89.25	$89.25	$89.30
Purchase #2	$111.63	13.602%	$126.8139	$126.81	$126.80	$126.80
Purchase #3	$235.97	13.713%	$268.3286	$268.33	$268.35	$268.30
Purchase #4	$173.88	8.464%	$188.5972	$188.60	$188.60	$188.60
Purchase #5	$225.51	13.195%	$255.266	$255.27	$255.25	$255.30
Purchase #6	$42.27	13.299%	$47.8915	$47.89	$47.90	$47.90
Purchase #7	$180.31	10.290%	$198.8639	$198.86	$198.85	$198.90
7 purchase totals =	$1,052.00		$1,175.0155	$1,175.01	$1,175.00	$1,175.10