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	$151.81	5.241%	$159.7664	$159.77	$159.75	$159.80
Purchase #2	$72.87	6.548%	$77.6415	$77.64	$77.65	$77.60
Purchase #3	$59.84	12.872%	$67.5426	$67.54	$67.55	$67.50
Purchase #4	$212.89	10.696%	$235.6607	$235.66	$235.65	$235.70
Purchase #5	$230.70	3.170%	$238.0132	$238.01	$238.00	$238.00
Purchase #6	$156.49	6.185%	$166.1689	$166.17	$166.15	$166.20
Purchase #7	$132.50	7.174%	$142.0056	$142.01	$142.00	$142.00
7 purchase totals =	$1,017.10		$1,086.7989	$1,086.80	$1,086.75	$1,086.80