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	$175.39	8.568%	$190.4174	$190.42	$190.40	$190.40
Purchase #2	$183.95	8.518%	$199.6189	$199.62	$199.60	$199.60
Purchase #3	$231.98	13.743%	$263.861	$263.86	$263.85	$263.90
Purchase #4	$242.40	4.501%	$253.3104	$253.31	$253.30	$253.30
Purchase #5	$127.71	3.302%	$131.927	$131.93	$131.95	$131.90
Purchase #6	$250.44	3.547%	$259.3231	$259.32	$259.30	$259.30
Purchase #7	$73.35	4.713%	$76.807	$76.81	$76.80	$76.80
7 purchase totals =	$1,285.22		$1,375.2648	$1,375.27	$1,375.20	$1,375.20