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	$171.71	13.345%	$194.6247	$194.62	$194.60	$194.60
Purchase #2	$222.53	10.788%	$246.5365	$246.54	$246.55	$246.50
Purchase #3	$45.36	4.794%	$47.5346	$47.53	$47.55	$47.50
Purchase #4	$56.61	6.555%	$60.3208	$60.32	$60.30	$60.30
Purchase #5	$68.98	12.368%	$77.5114	$77.51	$77.50	$77.50
Purchase #6	$34.67	11.816%	$38.7666	$38.77	$38.75	$38.80
Purchase #7	$90.39	10.752%	$100.1087	$100.11	$100.10	$100.10
7 purchase totals =	$690.25		$765.4033	$765.40	$765.35	$765.30