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	$180.87	5.535%	$190.8812	$190.88	$190.90	$190.90
Purchase #2	$148.63	7.575%	$159.8887	$159.89	$159.90	$159.90
Purchase #3	$103.27	11.129%	$114.7629	$114.76	$114.75	$114.80
Purchase #4	$122.25	6.269%	$129.9139	$129.91	$129.90	$129.90
Purchase #5	$31.61	3.379%	$32.6781	$32.68	$32.70	$32.70
Purchase #6	$85.58	5.524%	$90.3074	$90.31	$90.30	$90.30
Purchase #7	$43.42	3.124%	$44.7764	$44.78	$44.80	$44.80
7 purchase totals =	$715.63		$763.2086	$763.21	$763.25	$763.30