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	$99.66	7.787%	$107.4205	$107.42	$107.40	$107.40
Purchase #2	$47.49	13.178%	$53.7482	$53.75	$53.75	$53.70
Purchase #3	$160.86	4.202%	$167.6193	$167.62	$167.60	$167.60
Purchase #4	$127.63	12.392%	$143.4459	$143.45	$143.45	$143.40
Purchase #5	$208.37	6.762%	$222.46	$222.46	$222.45	$222.50
Purchase #6	$61.50	13.103%	$69.5583	$69.56	$69.55	$69.60
Purchase #7	$245.29	9.476%	$268.5337	$268.53	$268.55	$268.50
7 purchase totals =	$950.80		$1,032.7859	$1,032.79	$1,032.75	$1,032.70