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	$118.77	4.451%	$124.0565	$124.06	$124.05	$124.10
Purchase #2	$40.28	4.361%	$42.0366	$42.04	$42.05	$42.00
Purchase #3	$36.91	11.822%	$41.2735	$41.27	$41.25	$41.30
Purchase #4	$69.86	12.289%	$78.4451	$78.45	$78.45	$78.40
Purchase #5	$85.81	13.737%	$97.5977	$97.60	$97.60	$97.60
Purchase #6	$148.97	4.595%	$155.8152	$155.82	$155.80	$155.80
Purchase #7	$163.60	5.614%	$172.7845	$172.78	$172.80	$172.80
7 purchase totals =	$664.20		$712.0091	$712.02	$712.00	$712.00