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	$209.28	9.846%	$229.8857	$229.89	$229.90	$229.90
Purchase #2	$112.26	13.546%	$127.4667	$127.47	$127.45	$127.50
Purchase #3	$168.47	13.626%	$191.4257	$191.43	$191.45	$191.40
Purchase #4	$23.76	3.683%	$24.6351	$24.64	$24.65	$24.60
Purchase #5	$74.96	6.595%	$79.9036	$79.90	$79.90	$79.90
Purchase #6	$43.94	4.275%	$45.8184	$45.82	$45.80	$45.80
Purchase #7	$36.73	3.850%	$38.1441	$38.14	$38.15	$38.10
7 purchase totals =	$669.40		$737.2793	$737.29	$737.30	$737.20