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	$139.86	5.498%	$147.5495	$147.55	$147.55	$147.50
Purchase #2	$215.79	8.211%	$233.5085	$233.51	$233.50	$233.50
Purchase #3	$85.83	13.389%	$97.3218	$97.32	$97.30	$97.30
Purchase #4	$141.36	9.536%	$154.8401	$154.84	$154.85	$154.80
Purchase #5	$247.32	12.304%	$277.7503	$277.75	$277.75	$277.80
Purchase #6	$6.40	7.871%	$6.9037	$6.90	$6.90	$6.90
Purchase #7	$82.79	8.403%	$89.7468	$89.75	$89.75	$89.70
7 purchase totals =	$919.35		$1,007.6207	$1,007.62	$1,007.60	$1,007.50