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	$99.37	5.579%	$104.9139	$104.91	$104.90	$104.90
Purchase #2	$43.37	10.804%	$48.0557	$48.06	$48.05	$48.10
Purchase #3	$73.63	6.682%	$78.55	$78.55	$78.55	$78.60
Purchase #4	$178.52	10.316%	$196.9361	$196.94	$196.95	$196.90
Purchase #5	$48.35	3.623%	$50.1017	$50.10	$50.10	$50.10
Purchase #6	$136.25	11.783%	$152.3043	$152.30	$152.30	$152.30
Purchase #7	$230.31	6.314%	$244.8518	$244.85	$244.85	$244.90
7 purchase totals =	$809.80		$875.7135	$875.71	$875.70	$875.80