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	$236.82	10.799%	$262.3942	$262.39	$262.40	$262.40
Purchase #2	$179.26	9.794%	$196.8167	$196.82	$196.80	$196.80
Purchase #3	$203.60	12.659%	$229.3737	$229.37	$229.35	$229.40
Purchase #4	$39.39	9.807%	$43.253	$43.25	$43.25	$43.30
Purchase #5	$55.77	7.122%	$59.7419	$59.74	$59.75	$59.70
Purchase #6	$14.27	10.194%	$15.7247	$15.72	$15.70	$15.70
Purchase #7	$92.38	7.573%	$99.3759	$99.38	$99.40	$99.40
7 purchase totals =	$821.49		$906.6801	$906.67	$906.65	$906.70