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	$59.62	3.481%	$61.6954	$61.70	$61.70	$61.70
Purchase #2	$56.80	4.498%	$59.3549	$59.35	$59.35	$59.40
Purchase #3	$98.52	13.349%	$111.6714	$111.67	$111.65	$111.70
Purchase #4	$161.47	10.731%	$178.7973	$178.80	$178.80	$178.80
Purchase #5	$189.83	13.343%	$215.159	$215.16	$215.15	$215.20
Purchase #6	$32.39	13.237%	$36.6775	$36.68	$36.70	$36.70
Purchase #7	$183.30	9.215%	$200.1911	$200.19	$200.20	$200.20
7 purchase totals =	$781.93		$863.5466	$863.55	$863.55	$863.70