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	$58.86	6.567%	$62.7253	$62.73	$62.75	$62.70
Purchase #2	$151.27	10.152%	$166.6269	$166.63	$166.65	$166.60
Purchase #3	$226.30	10.398%	$249.8307	$249.83	$249.85	$249.80
Purchase #4	$159.96	13.384%	$181.369	$181.37	$181.35	$181.40
Purchase #5	$63.38	7.153%	$67.9136	$67.91	$67.90	$67.90
Purchase #6	$205.74	10.334%	$227.0012	$227.00	$227.00	$227.00
Purchase #7	$46.34	4.654%	$48.4967	$48.50	$48.50	$48.50
7 purchase totals =	$911.85		$1,003.9634	$1,003.97	$1,004.00	$1,003.90