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	$9.78	3.265%	$10.0993	$10.10	$10.10	$10.10
Purchase #2	$42.25	12.743%	$47.6339	$47.63	$47.65	$47.60
Purchase #3	$176.47	10.781%	$195.4952	$195.50	$195.50	$195.50
Purchase #4	$157.57	3.175%	$162.5728	$162.57	$162.55	$162.60
Purchase #5	$72.34	6.474%	$77.0233	$77.02	$77.00	$77.00
Purchase #6	$36.51	3.691%	$37.8576	$37.86	$37.85	$37.90
Purchase #7	$178.37	7.541%	$191.8209	$191.82	$191.80	$191.80
7 purchase totals =	$673.29		$722.5030	$722.50	$722.45	$722.50