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	$55.68	5.376%	$58.6734	$58.67	$58.65	$58.70
Purchase #2	$140.95	4.500%	$147.2928	$147.29	$147.30	$147.30
Purchase #3	$134.42	12.268%	$150.9106	$150.91	$150.90	$150.90
Purchase #4	$128.52	9.572%	$140.8219	$140.82	$140.80	$140.80
Purchase #5	$184.25	6.856%	$196.8822	$196.88	$196.90	$196.90
Purchase #6	$47.79	9.470%	$52.3157	$52.32	$52.30	$52.30
Purchase #7	$39.94	8.822%	$43.4635	$43.46	$43.45	$43.50
7 purchase totals =	$731.55		$790.3601	$790.35	$790.30	$790.40