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	$153.42	5.437%	$161.7614	$161.76	$161.75	$161.80
Purchase #2	$249.48	9.598%	$273.4251	$273.43	$273.45	$273.40
Purchase #3	$107.86	4.312%	$112.5109	$112.51	$112.50	$112.50
Purchase #4	$207.61	3.345%	$214.5546	$214.55	$214.55	$214.60
Purchase #5	$59.34	5.148%	$62.3948	$62.39	$62.40	$62.40
Purchase #6	$112.82	12.650%	$127.0917	$127.09	$127.10	$127.10
Purchase #7	$150.94	12.108%	$169.2158	$169.22	$169.20	$169.20
7 purchase totals =	$1,041.47		$1,120.9543	$1,120.95	$1,120.95	$1,121.00