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	$137.60	6.132%	$146.0376	$146.04	$146.05	$146.00
Purchase #2	$193.51	5.359%	$203.8802	$203.88	$203.90	$203.90
Purchase #3	$137.94	13.298%	$156.2833	$156.28	$156.30	$156.30
Purchase #4	$173.78	12.867%	$196.1403	$196.14	$196.15	$196.10
Purchase #5	$82.27	3.425%	$85.0877	$85.09	$85.10	$85.10
Purchase #6	$130.43	9.173%	$142.3943	$142.39	$142.40	$142.40
Purchase #7	$98.95	6.653%	$105.5331	$105.53	$105.55	$105.50
7 purchase totals =	$954.48		$1,035.3565	$1,035.35	$1,035.45	$1,035.30