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	$87.55	12.336%	$98.3502	$98.35	$98.35	$98.40
Purchase #2	$89.90	11.832%	$100.537	$100.54	$100.55	$100.50
Purchase #3	$96.88	6.843%	$103.5095	$103.51	$103.50	$103.50
Purchase #4	$218.31	12.424%	$245.4328	$245.43	$245.45	$245.40
Purchase #5	$87.60	13.353%	$99.2972	$99.30	$99.30	$99.30
Purchase #6	$183.67	6.569%	$195.7353	$195.74	$195.75	$195.70
Purchase #7	$112.71	6.602%	$120.1511	$120.15	$120.15	$120.20
7 purchase totals =	$876.62		$963.0131	$963.02	$963.05	$963.00