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	$102.59	12.651%	$115.5687	$115.57	$115.55	$115.60
Purchase #2	$5.55	13.216%	$6.2835	$6.28	$6.30	$6.30
Purchase #3	$69.96	11.740%	$78.1733	$78.17	$78.15	$78.20
Purchase #4	$142.88	10.789%	$158.2953	$158.30	$158.30	$158.30
Purchase #5	$227.60	12.683%	$256.4665	$256.47	$256.45	$256.50
Purchase #6	$101.40	7.693%	$109.2007	$109.20	$109.20	$109.20
Purchase #7	$48.96	3.268%	$50.56	$50.56	$50.55	$50.60
7 purchase totals =	$698.94		$774.5480	$774.55	$774.50	$774.70