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	$204.39	5.338%	$215.3003	$215.30	$215.30	$215.30
Purchase #2	$100.25	6.134%	$106.3993	$106.40	$106.40	$106.40
Purchase #3	$164.98	4.237%	$171.9702	$171.97	$171.95	$172.00
Purchase #4	$135.47	4.691%	$141.8249	$141.82	$141.80	$141.80
Purchase #5	$97.38	3.505%	$100.7932	$100.79	$100.80	$100.80
Purchase #6	$7.59	3.168%	$7.8305	$7.83	$7.85	$7.80
Purchase #7	$213.96	3.541%	$221.5363	$221.54	$221.55	$221.50
7 purchase totals =	$924.02		$965.6547	$965.65	$965.65	$965.60