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	$177.56	5.242%	$186.8677	$186.87	$186.85	$186.90
Purchase #2	$170.86	8.104%	$184.7065	$184.71	$184.70	$184.70
Purchase #3	$237.45	10.528%	$262.4487	$262.45	$262.45	$262.40
Purchase #4	$112.41	5.191%	$118.2452	$118.25	$118.25	$118.20
Purchase #5	$186.65	11.760%	$208.6	$208.60	$208.60	$208.60
Purchase #6	$179.94	3.829%	$186.8299	$186.83	$186.85	$186.80
Purchase #7	$73.98	11.663%	$82.6083	$82.61	$82.60	$82.60
7 purchase totals =	$1,138.85		$1,230.3063	$1,230.32	$1,230.30	$1,230.20