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	$181.31	10.150%	$199.713	$199.71	$199.70	$199.70
Purchase #2	$106.37	13.277%	$120.4927	$120.49	$120.50	$120.50
Purchase #3	$148.95	4.811%	$156.116	$156.12	$156.10	$156.10
Purchase #4	$112.43	11.681%	$125.5629	$125.56	$125.55	$125.60
Purchase #5	$216.68	4.256%	$225.9019	$225.90	$225.90	$225.90
Purchase #6	$78.51	12.726%	$88.5012	$88.50	$88.50	$88.50
Purchase #7	$189.87	3.586%	$196.6787	$196.68	$196.70	$196.70
7 purchase totals =	$1,034.12		$1,112.9664	$1,112.96	$1,112.95	$1,113.00