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	$203.60	9.234%	$222.4004	$222.40	$222.40	$222.40
Purchase #2	$144.25	10.638%	$159.5953	$159.60	$159.60	$159.60
Purchase #3	$145.54	4.107%	$151.5173	$151.52	$151.50	$151.50
Purchase #4	$70.54	4.510%	$73.7214	$73.72	$73.70	$73.70
Purchase #5	$186.88	7.498%	$200.8923	$200.89	$200.90	$200.90
Purchase #6	$182.34	12.258%	$204.6912	$204.69	$204.70	$204.70
Purchase #7	$206.73	12.535%	$232.6436	$232.64	$232.65	$232.60
7 purchase totals =	$1,139.88		$1,245.4615	$1,245.46	$1,245.45	$1,245.40