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	$99.29	3.183%	$102.4504	$102.45	$102.45	$102.50
Purchase #2	$151.71	7.127%	$162.5224	$162.52	$162.50	$162.50
Purchase #3	$133.70	8.398%	$144.9281	$144.93	$144.95	$144.90
Purchase #4	$191.42	9.833%	$210.2423	$210.24	$210.25	$210.20
Purchase #5	$38.79	8.716%	$42.1709	$42.17	$42.15	$42.20
Purchase #6	$113.33	11.653%	$126.5363	$126.54	$126.55	$126.50
Purchase #7	$160.36	11.556%	$178.8912	$178.89	$178.90	$178.90
7 purchase totals =	$888.60		$967.7416	$967.74	$967.75	$967.70