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	$107.48	6.444%	$114.406	$114.41	$114.40	$114.40
Purchase #2	$174.65	7.262%	$187.3331	$187.33	$187.35	$187.30
Purchase #3	$184.70	11.285%	$205.5434	$205.54	$205.55	$205.50
Purchase #4	$185.90	6.600%	$198.1694	$198.17	$198.15	$198.20
Purchase #5	$108.78	7.214%	$116.6274	$116.63	$116.65	$116.60
Purchase #6	$136.40	7.274%	$146.3217	$146.32	$146.30	$146.30
Purchase #7	$189.31	11.727%	$211.5104	$211.51	$211.50	$211.50
7 purchase totals =	$1,087.22		$1,179.9114	$1,179.91	$1,179.90	$1,179.80