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	$114.78	7.649%	$123.5595	$123.56	$123.55	$123.60
Purchase #2	$167.81	4.207%	$174.8698	$174.87	$174.85	$174.90
Purchase #3	$165.55	11.470%	$184.5386	$184.54	$184.55	$184.50
Purchase #4	$156.37	5.644%	$165.1955	$165.20	$165.20	$165.20
Purchase #5	$190.65	4.474%	$199.1797	$199.18	$199.20	$199.20
Purchase #6	$134.56	7.357%	$144.4596	$144.46	$144.45	$144.50
Purchase #7	$242.87	5.251%	$255.6231	$255.62	$255.60	$255.60
7 purchase totals =	$1,172.59		$1,247.4258	$1,247.43	$1,247.40	$1,247.50