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	$201.59	8.229%	$218.1788	$218.18	$218.20	$218.20
Purchase #2	$121.52	5.236%	$127.8828	$127.88	$127.90	$127.90
Purchase #3	$227.81	6.742%	$243.169	$243.17	$243.15	$243.20
Purchase #4	$90.57	6.622%	$96.5675	$96.57	$96.55	$96.60
Purchase #5	$61.40	6.382%	$65.3185	$65.32	$65.30	$65.30
Purchase #6	$8.43	4.791%	$8.8339	$8.83	$8.85	$8.80
Purchase #7	$223.32	11.667%	$249.3747	$249.37	$249.35	$249.40
7 purchase totals =	$934.64		$1,009.3252	$1,009.32	$1,009.30	$1,009.40