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	$105.89	6.656%	$112.938	$112.94	$112.95	$112.90
Purchase #2	$213.68	4.746%	$223.8213	$223.82	$223.80	$223.80
Purchase #3	$240.32	9.308%	$262.689	$262.69	$262.70	$262.70
Purchase #4	$49.33	11.241%	$54.8752	$54.88	$54.90	$54.90
Purchase #5	$72.42	6.562%	$77.1722	$77.17	$77.15	$77.20
Purchase #6	$228.79	3.186%	$236.0792	$236.08	$236.10	$236.10
Purchase #7	$154.58	6.815%	$165.1146	$165.11	$165.10	$165.10
7 purchase totals =	$1,065.01		$1,132.6895	$1,132.69	$1,132.70	$1,132.70