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	$167.44	10.812%	$185.5436	$185.54	$185.55	$185.50
Purchase #2	$78.27	5.802%	$82.8112	$82.81	$82.80	$82.80
Purchase #3	$159.38	3.615%	$165.1416	$165.14	$165.15	$165.10
Purchase #4	$5.89	3.454%	$6.0934	$6.09	$6.10	$6.10
Purchase #5	$214.31	9.564%	$234.8066	$234.81	$234.80	$234.80
Purchase #6	$98.29	10.174%	$108.29	$108.29	$108.30	$108.30
Purchase #7	$121.67	12.562%	$136.9542	$136.95	$136.95	$137.00
7 purchase totals =	$845.25		$919.6406	$919.63	$919.65	$919.60