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	$92.37	7.823%	$99.5961	$99.60	$99.60	$99.60
Purchase #2	$72.49	7.689%	$78.0638	$78.06	$78.05	$78.10
Purchase #3	$133.53	5.136%	$140.3881	$140.39	$140.40	$140.40
Purchase #4	$146.93	12.236%	$164.9084	$164.91	$164.90	$164.90
Purchase #5	$236.27	5.364%	$248.9435	$248.94	$248.95	$248.90
Purchase #6	$250.46	12.860%	$282.6692	$282.67	$282.65	$282.70
Purchase #7	$97.65	11.179%	$108.5663	$108.57	$108.55	$108.60
7 purchase totals =	$1,029.70		$1,123.1354	$1,123.14	$1,123.10	$1,123.20