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	$222.33	12.172%	$249.392	$249.39	$249.40	$249.40
Purchase #2	$16.41	12.564%	$18.4718	$18.47	$18.45	$18.50
Purchase #3	$81.95	10.759%	$90.767	$90.77	$90.75	$90.80
Purchase #4	$239.65	12.464%	$269.52	$269.52	$269.50	$269.50
Purchase #5	$134.94	8.256%	$146.0806	$146.08	$146.10	$146.10
Purchase #6	$135.32	9.569%	$148.2688	$148.27	$148.25	$148.30
Purchase #7	$156.89	6.318%	$166.8023	$166.80	$166.80	$166.80
7 purchase totals =	$987.49		$1,089.3025	$1,089.30	$1,089.25	$1,089.40