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	$204.40	7.661%	$220.0591	$220.06	$220.05	$220.10
Purchase #2	$228.93	8.212%	$247.7297	$247.73	$247.75	$247.70
Purchase #3	$132.43	9.119%	$144.5063	$144.51	$144.50	$144.50
Purchase #4	$101.86	9.370%	$111.4043	$111.40	$111.40	$111.40
Purchase #5	$178.89	9.188%	$195.3264	$195.33	$195.35	$195.30
Purchase #6	$30.88	12.612%	$34.7746	$34.77	$34.75	$34.80
Purchase #7	$145.50	7.320%	$156.1506	$156.15	$156.15	$156.20
7 purchase totals =	$1,022.89		$1,109.9510	$1,109.95	$1,109.95	$1,110.00