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	$54.27	9.558%	$59.4571	$59.46	$59.45	$59.50
Purchase #2	$227.63	13.667%	$258.7402	$258.74	$258.75	$258.70
Purchase #3	$114.37	9.215%	$124.9092	$124.91	$124.90	$124.90
Purchase #4	$212.50	7.479%	$228.3929	$228.39	$228.40	$228.40
Purchase #5	$135.63	6.193%	$144.0296	$144.03	$144.05	$144.00
Purchase #6	$242.86	7.641%	$261.4169	$261.42	$261.40	$261.40
Purchase #7	$104.62	3.675%	$108.4648	$108.46	$108.45	$108.50
7 purchase totals =	$1,091.88		$1,185.4107	$1,185.41	$1,185.40	$1,185.40