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	$64.28	13.368%	$72.873	$72.87	$72.85	$72.90
Purchase #2	$134.28	7.359%	$144.1617	$144.16	$144.15	$144.20
Purchase #3	$144.98	13.174%	$164.0797	$164.08	$164.10	$164.10
Purchase #4	$93.44	5.642%	$98.7119	$98.71	$98.70	$98.70
Purchase #5	$109.83	13.686%	$124.8613	$124.86	$124.85	$124.90
Purchase #6	$144.61	9.265%	$158.0081	$158.01	$158.00	$158.00
Purchase #7	$154.39	9.133%	$168.4904	$168.49	$168.50	$168.50
7 purchase totals =	$845.81		$931.1861	$931.18	$931.15	$931.30