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	$209.54	6.251%	$222.6383	$222.64	$222.65	$222.60
Purchase #2	$207.64	12.432%	$233.4538	$233.45	$233.45	$233.50
Purchase #3	$11.43	9.602%	$12.5275	$12.53	$12.55	$12.50
Purchase #4	$65.53	11.347%	$72.9657	$72.97	$72.95	$73.00
Purchase #5	$63.87	11.151%	$70.9921	$70.99	$71.00	$71.00
Purchase #6	$51.54	4.296%	$53.7542	$53.75	$53.75	$53.80
Purchase #7	$71.62	10.118%	$78.8665	$78.87	$78.85	$78.90
7 purchase totals =	$681.17		$745.1981	$745.20	$745.20	$745.30