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	$118.89	10.641%	$131.5411	$131.54	$131.55	$131.50
Purchase #2	$80.51	3.682%	$83.4744	$83.47	$83.45	$83.50
Purchase #3	$27.34	13.804%	$31.114	$31.11	$31.10	$31.10
Purchase #4	$21.50	10.156%	$23.6835	$23.68	$23.70	$23.70
Purchase #5	$240.65	12.815%	$271.4893	$271.49	$271.50	$271.50
Purchase #6	$79.88	13.463%	$90.6342	$90.63	$90.65	$90.60
Purchase #7	$95.82	7.168%	$102.6884	$102.69	$102.70	$102.70
7 purchase totals =	$664.59		$734.6249	$734.61	$734.65	$734.60