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	$69.31	4.524%	$72.4456	$72.45	$72.45	$72.40
Purchase #2	$120.57	5.809%	$127.5739	$127.57	$127.55	$127.60
Purchase #3	$118.33	5.630%	$124.992	$124.99	$125.00	$125.00
Purchase #4	$124.32	5.784%	$131.5107	$131.51	$131.50	$131.50
Purchase #5	$197.94	8.677%	$215.1153	$215.12	$215.10	$215.10
Purchase #6	$120.54	9.426%	$131.9021	$131.90	$131.90	$131.90
Purchase #7	$20.91	13.278%	$23.6864	$23.69	$23.70	$23.70
7 purchase totals =	$771.92		$827.2260	$827.23	$827.20	$827.20