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	$136.48	11.556%	$152.2516	$152.25	$152.25	$152.30
Purchase #2	$96.40	4.461%	$100.7004	$100.70	$100.70	$100.70
Purchase #3	$200.26	5.815%	$211.9051	$211.91	$211.90	$211.90
Purchase #4	$22.74	5.178%	$23.9175	$23.92	$23.90	$23.90
Purchase #5	$98.65	10.112%	$108.6255	$108.63	$108.65	$108.60
Purchase #6	$98.66	6.287%	$104.8628	$104.86	$104.85	$104.90
Purchase #7	$79.50	7.715%	$85.6334	$85.63	$85.65	$85.60
7 purchase totals =	$732.69		$787.8963	$787.90	$787.90	$787.90