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	$42.86	6.481%	$45.6378	$45.64	$45.65	$45.60
Purchase #2	$135.97	3.815%	$141.1573	$141.16	$141.15	$141.20
Purchase #3	$11.27	13.270%	$12.7655	$12.77	$12.75	$12.80
Purchase #4	$191.53	11.392%	$213.3491	$213.35	$213.35	$213.30
Purchase #5	$152.71	8.446%	$165.6079	$165.61	$165.60	$165.60
Purchase #6	$238.85	4.424%	$249.4167	$249.42	$249.40	$249.40
Purchase #7	$179.58	6.226%	$190.7607	$190.76	$190.75	$190.80
7 purchase totals =	$952.77		$1,018.6950	$1,018.71	$1,018.65	$1,018.70