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	$117.92	13.399%	$133.7201	$133.72	$133.70	$133.70
Purchase #2	$100.56	10.178%	$110.795	$110.80	$110.80	$110.80
Purchase #3	$227.86	5.423%	$240.2168	$240.22	$240.20	$240.20
Purchase #4	$55.33	3.469%	$57.2494	$57.25	$57.25	$57.20
Purchase #5	$78.95	4.260%	$82.3133	$82.31	$82.30	$82.30
Purchase #6	$198.43	8.688%	$215.6696	$215.67	$215.65	$215.70
Purchase #7	$247.58	6.466%	$263.5885	$263.59	$263.60	$263.60
7 purchase totals =	$1,026.63		$1,103.5527	$1,103.56	$1,103.50	$1,103.50