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	$68.48	4.404%	$71.4959	$71.50	$71.50	$71.50
Purchase #2	$218.97	12.147%	$245.5683	$245.57	$245.55	$245.60
Purchase #3	$248.51	8.702%	$270.1353	$270.14	$270.15	$270.10
Purchase #4	$78.92	8.135%	$85.3401	$85.34	$85.35	$85.30
Purchase #5	$64.25	3.515%	$66.5084	$66.51	$66.50	$66.50
Purchase #6	$159.72	9.387%	$174.7129	$174.71	$174.70	$174.70
Purchase #7	$36.81	9.407%	$40.2727	$40.27	$40.25	$40.30
7 purchase totals =	$875.66		$954.0336	$954.04	$954.00	$954.00