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	$173.51	4.709%	$181.6806	$181.68	$181.70	$181.70
Purchase #2	$248.53	11.487%	$277.0786	$277.08	$277.10	$277.10
Purchase #3	$104.76	10.256%	$115.5042	$115.50	$115.50	$115.50
Purchase #4	$33.96	9.137%	$37.0629	$37.06	$37.05	$37.10
Purchase #5	$142.81	9.853%	$156.8811	$156.88	$156.90	$156.90
Purchase #6	$235.90	8.734%	$256.5035	$256.50	$256.50	$256.50
Purchase #7	$155.38	3.580%	$160.9426	$160.94	$160.95	$160.90
7 purchase totals =	$1,094.85		$1,185.6535	$1,185.64	$1,185.70	$1,185.70