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	$57.83	5.790%	$61.1784	$61.18	$61.20	$61.20
Purchase #2	$218.43	12.127%	$244.919	$244.92	$244.90	$244.90
Purchase #3	$13.86	10.158%	$15.2679	$15.27	$15.25	$15.30
Purchase #4	$36.25	3.222%	$37.418	$37.42	$37.40	$37.40
Purchase #5	$170.27	3.483%	$176.2005	$176.20	$176.20	$176.20
Purchase #6	$29.30	7.730%	$31.5649	$31.56	$31.55	$31.60
Purchase #7	$99.78	6.140%	$105.9065	$105.91	$105.90	$105.90
7 purchase totals =	$625.72		$672.4552	$672.46	$672.40	$672.50