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	$127.62	11.789%	$142.6651	$142.67	$142.65	$142.70
Purchase #2	$48.63	6.223%	$51.6562	$51.66	$51.65	$51.70
Purchase #3	$72.37	5.633%	$76.4466	$76.45	$76.45	$76.40
Purchase #4	$30.54	3.253%	$31.5335	$31.53	$31.55	$31.50
Purchase #5	$166.42	10.590%	$184.0439	$184.04	$184.05	$184.00
Purchase #6	$235.77	3.371%	$243.7178	$243.72	$243.70	$243.70
Purchase #7	$118.49	8.461%	$128.5154	$128.52	$128.50	$128.50
7 purchase totals =	$799.84		$858.5785	$858.59	$858.55	$858.50