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	$48.70	10.538%	$53.832	$53.83	$53.85	$53.80
Purchase #2	$93.30	9.610%	$102.2661	$102.27	$102.25	$102.30
Purchase #3	$55.44	10.830%	$61.4442	$61.44	$61.45	$61.40
Purchase #4	$220.48	4.288%	$229.9342	$229.93	$229.95	$229.90
Purchase #5	$157.88	6.703%	$168.4627	$168.46	$168.45	$168.50
Purchase #6	$98.33	13.220%	$111.3292	$111.33	$111.35	$111.30
Purchase #7	$107.58	4.688%	$112.6234	$112.62	$112.60	$112.60
7 purchase totals =	$781.71		$839.8918	$839.88	$839.90	$839.80