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	$48.98	12.394%	$55.0506	$55.05	$55.05	$55.10
Purchase #2	$208.94	6.222%	$221.9402	$221.94	$221.95	$221.90
Purchase #3	$94.63	11.173%	$105.203	$105.20	$105.20	$105.20
Purchase #4	$191.83	10.590%	$212.1448	$212.14	$212.15	$212.10
Purchase #5	$184.88	13.365%	$209.5892	$209.59	$209.60	$209.60
Purchase #6	$237.93	3.129%	$245.3748	$245.37	$245.35	$245.40
Purchase #7	$124.70	5.630%	$131.7206	$131.72	$131.70	$131.70
7 purchase totals =	$1,091.89		$1,181.0232	$1,181.01	$1,181.00	$1,181.00