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	$56.38	8.779%	$61.3296	$61.33	$61.35	$61.30
Purchase #2	$51.62	5.744%	$54.5851	$54.59	$54.60	$54.60
Purchase #3	$186.80	7.331%	$200.4943	$200.49	$200.50	$200.50
Purchase #4	$107.86	9.412%	$118.0118	$118.01	$118.00	$118.00
Purchase #5	$64.93	3.590%	$67.261	$67.26	$67.25	$67.30
Purchase #6	$193.89	8.144%	$209.6804	$209.68	$209.70	$209.70
Purchase #7	$33.84	13.433%	$38.3857	$38.39	$38.40	$38.40
7 purchase totals =	$695.32		$749.7479	$749.75	$749.80	$749.80