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	$54.98	3.430%	$56.8658	$56.87	$56.85	$56.90
Purchase #2	$196.92	12.823%	$222.1711	$222.17	$222.15	$222.20
Purchase #3	$135.35	3.684%	$140.3363	$140.34	$140.35	$140.30
Purchase #4	$201.74	3.617%	$209.0369	$209.04	$209.05	$209.00
Purchase #5	$228.32	4.639%	$238.9118	$238.91	$238.90	$238.90
Purchase #6	$31.29	4.165%	$32.5932	$32.59	$32.60	$32.60
Purchase #7	$241.97	3.624%	$250.739	$250.74	$250.75	$250.70
7 purchase totals =	$1,090.57		$1,150.6541	$1,150.66	$1,150.65	$1,150.60