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	$76.59	9.108%	$83.5658	$83.57	$83.55	$83.60
Purchase #2	$174.59	5.534%	$184.2518	$184.25	$184.25	$184.30
Purchase #3	$21.77	7.214%	$23.3405	$23.34	$23.35	$23.30
Purchase #4	$55.26	7.160%	$59.2166	$59.22	$59.20	$59.20
Purchase #5	$57.34	3.330%	$59.2494	$59.25	$59.25	$59.20
Purchase #6	$138.30	9.479%	$151.4095	$151.41	$151.40	$151.40
Purchase #7	$133.72	12.222%	$150.0633	$150.06	$150.05	$150.10
7 purchase totals =	$657.57		$711.0969	$711.10	$711.05	$711.10