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	$142.52	6.340%	$151.5558	$151.56	$151.55	$151.60
Purchase #2	$95.94	12.425%	$107.8605	$107.86	$107.85	$107.90
Purchase #3	$173.37	13.580%	$196.9136	$196.91	$196.90	$196.90
Purchase #4	$166.93	12.804%	$188.3037	$188.30	$188.30	$188.30
Purchase #5	$82.53	4.143%	$85.9492	$85.95	$85.95	$85.90
Purchase #6	$163.83	10.286%	$180.6816	$180.68	$180.70	$180.70
Purchase #7	$154.62	8.819%	$168.2559	$168.26	$168.25	$168.30
7 purchase totals =	$979.74		$1,079.5203	$1,079.52	$1,079.50	$1,079.60