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	$241.82	3.721%	$250.8181	$250.82	$250.80	$250.80
Purchase #2	$234.64	6.362%	$249.5678	$249.57	$249.55	$249.60
Purchase #3	$36.98	9.684%	$40.5611	$40.56	$40.55	$40.60
Purchase #4	$170.36	11.498%	$189.948	$189.95	$189.95	$189.90
Purchase #5	$78.41	10.116%	$86.342	$86.34	$86.35	$86.30
Purchase #6	$79.30	12.799%	$89.4496	$89.45	$89.45	$89.40
Purchase #7	$155.88	3.161%	$160.8074	$160.81	$160.80	$160.80
7 purchase totals =	$997.39		$1,067.4940	$1,067.50	$1,067.45	$1,067.40