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	$158.90	5.284%	$167.2963	$167.30	$167.30	$167.30
Purchase #2	$78.55	8.666%	$85.3571	$85.36	$85.35	$85.40
Purchase #3	$214.43	4.435%	$223.94	$223.94	$223.95	$223.90
Purchase #4	$179.30	4.624%	$187.5908	$187.59	$187.60	$187.60
Purchase #5	$127.95	8.123%	$138.3434	$138.34	$138.35	$138.30
Purchase #6	$230.72	8.857%	$251.1549	$251.15	$251.15	$251.20
Purchase #7	$25.70	8.465%	$27.8755	$27.88	$27.90	$27.90
7 purchase totals =	$1,015.55		$1,081.5580	$1,081.56	$1,081.60	$1,081.60