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	$188.97	13.844%	$215.131	$215.13	$215.15	$215.10
Purchase #2	$72.73	13.524%	$82.566	$82.57	$82.55	$82.60
Purchase #3	$94.61	13.574%	$107.4524	$107.45	$107.45	$107.50
Purchase #4	$56.26	3.859%	$58.4311	$58.43	$58.45	$58.40
Purchase #5	$183.92	12.715%	$207.3054	$207.31	$207.30	$207.30
Purchase #6	$82.68	8.230%	$89.4846	$89.48	$89.50	$89.50
Purchase #7	$222.34	7.710%	$239.4824	$239.48	$239.50	$239.50
7 purchase totals =	$901.51		$999.8529	$999.85	$999.90	$999.90