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	$51.59	11.250%	$57.3939	$57.39	$57.40	$57.40
Purchase #2	$178.79	3.478%	$185.0083	$185.01	$185.00	$185.00
Purchase #3	$89.90	11.596%	$100.3248	$100.32	$100.30	$100.30
Purchase #4	$140.93	12.280%	$158.2362	$158.24	$158.25	$158.20
Purchase #5	$24.30	3.215%	$25.0812	$25.08	$25.10	$25.10
Purchase #6	$182.44	3.191%	$188.2617	$188.26	$188.25	$188.30
Purchase #7	$141.43	6.831%	$151.0911	$151.09	$151.10	$151.10
7 purchase totals =	$809.38		$865.3972	$865.39	$865.40	$865.40