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	$107.68	7.256%	$115.4933	$115.49	$115.50	$115.50
Purchase #2	$142.55	5.579%	$150.5029	$150.50	$150.50	$150.50
Purchase #3	$184.46	9.228%	$201.482	$201.48	$201.50	$201.50
Purchase #4	$248.31	7.734%	$267.5143	$267.51	$267.50	$267.50
Purchase #5	$69.87	3.347%	$72.2085	$72.21	$72.20	$72.20
Purchase #6	$67.69	13.832%	$77.0529	$77.05	$77.05	$77.10
Purchase #7	$201.32	7.337%	$216.0908	$216.09	$216.10	$216.10
7 purchase totals =	$1,021.88		$1,100.3447	$1,100.33	$1,100.35	$1,100.40