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	$79.61	4.212%	$82.9632	$82.96	$82.95	$83.00
Purchase #2	$81.43	8.192%	$88.1007	$88.10	$88.10	$88.10
Purchase #3	$58.92	6.652%	$62.8394	$62.84	$62.85	$62.80
Purchase #4	$150.67	13.671%	$171.2681	$171.27	$171.25	$171.30
Purchase #5	$240.30	13.713%	$273.2523	$273.25	$273.25	$273.30
Purchase #6	$147.80	4.483%	$154.4259	$154.43	$154.45	$154.40
Purchase #7	$156.45	6.728%	$166.976	$166.98	$167.00	$167.00
7 purchase totals =	$915.18		$999.8256	$999.83	$999.85	$999.90