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	$81.97	5.486%	$86.4669	$86.47	$86.45	$86.50
Purchase #2	$48.44	12.606%	$54.5463	$54.55	$54.55	$54.50
Purchase #3	$149.62	8.467%	$162.2883	$162.29	$162.30	$162.30
Purchase #4	$174.87	8.605%	$189.9176	$189.92	$189.90	$189.90
Purchase #5	$185.95	10.424%	$205.3334	$205.33	$205.35	$205.30
Purchase #6	$138.70	12.865%	$156.5438	$156.54	$156.55	$156.50
Purchase #7	$187.92	4.506%	$196.3877	$196.39	$196.40	$196.40
7 purchase totals =	$967.47		$1,051.4840	$1,051.49	$1,051.50	$1,051.40