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	$33.30	9.769%	$36.5531	$36.55	$36.55	$36.60
Purchase #2	$206.75	4.506%	$216.0662	$216.07	$216.05	$216.10
Purchase #3	$170.50	8.696%	$185.3267	$185.33	$185.35	$185.30
Purchase #4	$71.59	6.509%	$76.2498	$76.25	$76.25	$76.20
Purchase #5	$210.90	5.651%	$222.818	$222.82	$222.80	$222.80
Purchase #6	$131.71	13.158%	$149.0404	$149.04	$149.05	$149.00
Purchase #7	$43.30	9.281%	$47.3187	$47.32	$47.30	$47.30
7 purchase totals =	$868.05		$933.3729	$933.38	$933.35	$933.30