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	$202.64	10.449%	$223.8139	$223.81	$223.80	$223.80
Purchase #2	$209.51	13.374%	$237.5299	$237.53	$237.55	$237.50
Purchase #3	$179.25	9.714%	$196.6623	$196.66	$196.65	$196.70
Purchase #4	$51.54	7.435%	$55.372	$55.37	$55.35	$55.40
Purchase #5	$224.94	9.750%	$246.8717	$246.87	$246.85	$246.90
Purchase #6	$142.61	6.363%	$151.6843	$151.68	$151.70	$151.70
Purchase #7	$71.61	9.279%	$78.2547	$78.25	$78.25	$78.30
7 purchase totals =	$1,082.10		$1,190.1888	$1,190.17	$1,190.15	$1,190.30