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	$60.76	10.392%	$67.0742	$67.07	$67.05	$67.10
Purchase #2	$237.89	3.365%	$245.895	$245.90	$245.90	$245.90
Purchase #3	$234.57	7.374%	$251.8672	$251.87	$251.85	$251.90
Purchase #4	$215.30	3.249%	$222.2951	$222.30	$222.30	$222.30
Purchase #5	$147.98	11.257%	$164.6381	$164.64	$164.65	$164.60
Purchase #6	$141.53	8.344%	$153.3393	$153.34	$153.35	$153.30
Purchase #7	$80.41	13.505%	$91.2694	$91.27	$91.25	$91.30
7 purchase totals =	$1,118.44		$1,196.3783	$1,196.39	$1,196.35	$1,196.40