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	$35.56	3.549%	$36.822	$36.82	$36.80	$36.80
Purchase #2	$199.56	10.657%	$220.8271	$220.83	$220.85	$220.80
Purchase #3	$140.92	9.437%	$154.2186	$154.22	$154.20	$154.20
Purchase #4	$122.88	3.501%	$127.182	$127.18	$127.20	$127.20
Purchase #5	$131.61	12.397%	$147.9257	$147.93	$147.95	$147.90
Purchase #6	$127.51	13.642%	$144.9049	$144.90	$144.90	$144.90
Purchase #7	$216.39	3.382%	$223.7083	$223.71	$223.70	$223.70
7 purchase totals =	$974.43		$1,055.5886	$1,055.59	$1,055.60	$1,055.50