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	$103.70	10.676%	$114.771	$114.77	$114.75	$114.80
Purchase #2	$160.76	7.757%	$173.2302	$173.23	$173.25	$173.20
Purchase #3	$28.31	3.489%	$29.2977	$29.30	$29.30	$29.30
Purchase #4	$131.71	7.748%	$141.9149	$141.91	$141.90	$141.90
Purchase #5	$86.54	6.835%	$92.455	$92.46	$92.45	$92.50
Purchase #6	$27.82	12.696%	$31.352	$31.35	$31.35	$31.40
Purchase #7	$144.74	4.633%	$151.4458	$151.45	$151.45	$151.40
7 purchase totals =	$683.58		$734.4666	$734.47	$734.45	$734.50