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	$50.99	12.628%	$57.429	$57.43	$57.45	$57.40
Purchase #2	$248.65	5.334%	$261.913	$261.91	$261.90	$261.90
Purchase #3	$54.84	12.564%	$61.7301	$61.73	$61.75	$61.70
Purchase #4	$99.80	4.399%	$104.1902	$104.19	$104.20	$104.20
Purchase #5	$186.75	5.415%	$196.8625	$196.86	$196.85	$196.90
Purchase #6	$38.55	6.574%	$41.0843	$41.08	$41.10	$41.10
Purchase #7	$156.79	12.369%	$176.1834	$176.18	$176.20	$176.20
7 purchase totals =	$836.37		$899.3925	$899.38	$899.45	$899.40