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	$75.78	13.411%	$85.9429	$85.94	$85.95	$85.90
Purchase #2	$40.28	5.872%	$42.6452	$42.65	$42.65	$42.60
Purchase #3	$138.79	3.656%	$143.8642	$143.86	$143.85	$143.90
Purchase #4	$96.54	5.554%	$101.9018	$101.90	$101.90	$101.90
Purchase #5	$245.91	7.621%	$264.6508	$264.65	$264.65	$264.70
Purchase #6	$72.80	13.856%	$82.8872	$82.89	$82.90	$82.90
Purchase #7	$97.36	5.355%	$102.5736	$102.57	$102.55	$102.60
7 purchase totals =	$767.46		$824.4657	$824.46	$824.45	$824.50