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	$125.67	13.261%	$142.3351	$142.34	$142.35	$142.30
Purchase #2	$164.40	13.506%	$186.6039	$186.60	$186.60	$186.60
Purchase #3	$55.57	4.792%	$58.2329	$58.23	$58.25	$58.20
Purchase #4	$134.54	4.564%	$140.6804	$140.68	$140.70	$140.70
Purchase #5	$75.30	4.265%	$78.5115	$78.51	$78.50	$78.50
Purchase #6	$219.93	4.740%	$230.3547	$230.35	$230.35	$230.40
Purchase #7	$245.64	7.539%	$264.1588	$264.16	$264.15	$264.20
7 purchase totals =	$1,021.05		$1,100.8773	$1,100.87	$1,100.90	$1,100.90