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	$209.48	7.306%	$224.7846	$224.78	$224.80	$224.80
Purchase #2	$46.33	7.393%	$49.7552	$49.76	$49.75	$49.80
Purchase #3	$115.74	10.601%	$128.0096	$128.01	$128.00	$128.00
Purchase #4	$65.54	7.630%	$70.5407	$70.54	$70.55	$70.50
Purchase #5	$78.57	13.768%	$89.3875	$89.39	$89.40	$89.40
Purchase #6	$241.32	11.515%	$269.108	$269.11	$269.10	$269.10
Purchase #7	$213.43	4.545%	$223.1304	$223.13	$223.15	$223.10
7 purchase totals =	$970.41		$1,054.7160	$1,054.72	$1,054.75	$1,054.70