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	$69.35	4.870%	$72.7273	$72.73	$72.75	$72.70
Purchase #2	$61.32	10.571%	$67.8021	$67.80	$67.80	$67.80
Purchase #3	$58.84	12.236%	$66.0397	$66.04	$66.05	$66.00
Purchase #4	$161.83	12.247%	$181.6493	$181.65	$181.65	$181.60
Purchase #5	$39.81	6.336%	$42.3324	$42.33	$42.35	$42.30
Purchase #6	$23.36	4.220%	$24.3458	$24.35	$24.35	$24.30
Purchase #7	$51.82	7.755%	$55.8386	$55.84	$55.85	$55.80
7 purchase totals =	$466.33		$510.7352	$510.74	$510.80	$510.50