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	$97.97	11.840%	$109.5696	$109.57	$109.55	$109.60
Purchase #2	$201.65	11.343%	$224.5232	$224.52	$224.50	$224.50
Purchase #3	$5.91	10.735%	$6.5444	$6.54	$6.55	$6.50
Purchase #4	$143.29	6.737%	$152.9434	$152.94	$152.95	$152.90
Purchase #5	$221.46	9.556%	$242.6227	$242.62	$242.60	$242.60
Purchase #6	$123.29	3.749%	$127.9121	$127.91	$127.90	$127.90
Purchase #7	$74.76	8.502%	$81.1161	$81.12	$81.10	$81.10
7 purchase totals =	$868.33		$945.2315	$945.22	$945.15	$945.10