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	$159.54	10.133%	$175.7062	$175.71	$175.70	$175.70
Purchase #2	$37.72	7.676%	$40.6154	$40.62	$40.60	$40.60
Purchase #3	$165.93	5.198%	$174.555	$174.56	$174.55	$174.60
Purchase #4	$103.67	11.339%	$115.4251	$115.43	$115.45	$115.40
Purchase #5	$117.53	12.653%	$132.4011	$132.40	$132.40	$132.40
Purchase #6	$97.85	11.648%	$109.2476	$109.25	$109.25	$109.20
Purchase #7	$73.53	6.680%	$78.4418	$78.44	$78.45	$78.40
7 purchase totals =	$755.77		$826.3922	$826.41	$826.40	$826.30