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	$128.44	9.569%	$140.7304	$140.73	$140.75	$140.70
Purchase #2	$105.87	5.528%	$111.7225	$111.72	$111.70	$111.70
Purchase #3	$213.94	6.706%	$228.2868	$228.29	$228.30	$228.30
Purchase #4	$29.81	10.166%	$32.8405	$32.84	$32.85	$32.80
Purchase #5	$189.27	7.553%	$203.5656	$203.57	$203.55	$203.60
Purchase #6	$155.31	6.523%	$165.4409	$165.44	$165.45	$165.40
Purchase #7	$248.69	5.385%	$262.082	$262.08	$262.10	$262.10
7 purchase totals =	$1,071.33		$1,144.6687	$1,144.67	$1,144.70	$1,144.60