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	$203.44	10.560%	$224.9233	$224.92	$224.90	$224.90
Purchase #2	$69.78	12.794%	$78.7077	$78.71	$78.70	$78.70
Purchase #3	$103.63	7.823%	$111.737	$111.74	$111.75	$111.70
Purchase #4	$7.48	3.756%	$7.7609	$7.76	$7.75	$7.80
Purchase #5	$35.58	4.348%	$37.127	$37.13	$37.15	$37.10
Purchase #6	$194.96	6.464%	$207.5622	$207.56	$207.55	$207.60
Purchase #7	$21.67	12.754%	$24.4338	$24.43	$24.45	$24.40
7 purchase totals =	$636.54		$692.2519	$692.25	$692.25	$692.20