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	$199.63	10.462%	$220.5153	$220.52	$220.50	$220.50
Purchase #2	$23.25	4.361%	$24.2639	$24.26	$24.25	$24.30
Purchase #3	$49.78	5.187%	$52.3621	$52.36	$52.35	$52.40
Purchase #4	$76.41	8.504%	$82.9079	$82.91	$82.90	$82.90
Purchase #5	$71.38	10.286%	$78.7221	$78.72	$78.70	$78.70
Purchase #6	$71.78	5.816%	$75.9547	$75.95	$75.95	$76.00
Purchase #7	$162.65	6.470%	$173.1735	$173.17	$173.15	$173.20
7 purchase totals =	$654.88		$707.8995	$707.89	$707.80	$708.00