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	$167.32	4.544%	$174.923	$174.92	$174.90	$174.90
Purchase #2	$127.27	11.446%	$141.8373	$141.84	$141.85	$141.80
Purchase #3	$93.45	5.114%	$98.229	$98.23	$98.25	$98.20
Purchase #4	$140.60	12.736%	$158.5068	$158.51	$158.50	$158.50
Purchase #5	$43.68	11.382%	$48.6517	$48.65	$48.65	$48.70
Purchase #6	$80.76	12.603%	$90.9382	$90.94	$90.95	$90.90
Purchase #7	$6.41	4.687%	$6.7104	$6.71	$6.70	$6.70
7 purchase totals =	$659.49		$719.7964	$719.80	$719.80	$719.70