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	$54.56	5.211%	$57.4031	$57.40	$57.40	$57.40
Purchase #2	$180.35	3.478%	$186.6226	$186.62	$186.60	$186.60
Purchase #3	$83.46	13.378%	$94.6253	$94.63	$94.65	$94.60
Purchase #4	$198.54	12.230%	$222.8214	$222.82	$222.80	$222.80
Purchase #5	$243.61	12.176%	$273.272	$273.27	$273.25	$273.30
Purchase #6	$59.51	9.310%	$65.0504	$65.05	$65.05	$65.10
Purchase #7	$207.83	11.588%	$231.9133	$231.91	$231.90	$231.90
7 purchase totals =	$1,027.86		$1,131.7081	$1,131.70	$1,131.65	$1,131.70