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	$63.85	11.621%	$71.27	$71.27	$71.25	$71.30
Purchase #2	$73.55	8.692%	$79.943	$79.94	$79.95	$79.90
Purchase #3	$147.78	12.651%	$166.4756	$166.48	$166.50	$166.50
Purchase #4	$130.82	6.676%	$139.5535	$139.55	$139.55	$139.60
Purchase #5	$207.25	5.326%	$218.2881	$218.29	$218.30	$218.30
Purchase #6	$153.43	13.394%	$173.9804	$173.98	$174.00	$174.00
Purchase #7	$170.65	6.859%	$182.3549	$182.35	$182.35	$182.40
7 purchase totals =	$947.33		$1,031.8655	$1,031.86	$1,031.90	$1,032.00