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	$31.96	12.156%	$35.8451	$35.85	$35.85	$35.80
Purchase #2	$55.45	7.349%	$59.525	$59.53	$59.55	$59.50
Purchase #3	$138.56	8.512%	$150.3542	$150.35	$150.35	$150.40
Purchase #4	$56.36	13.387%	$63.9049	$63.90	$63.90	$63.90
Purchase #5	$42.48	7.219%	$45.5466	$45.55	$45.55	$45.50
Purchase #6	$76.85	12.591%	$86.5262	$86.53	$86.55	$86.50
Purchase #7	$47.27	13.298%	$53.556	$53.56	$53.55	$53.60
7 purchase totals =	$448.93		$495.2580	$495.27	$495.30	$495.20