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	$144.70	13.582%	$164.3532	$164.35	$164.35	$164.40
Purchase #2	$132.86	13.798%	$151.192	$151.19	$151.20	$151.20
Purchase #3	$247.53	12.158%	$277.6247	$277.62	$277.60	$277.60
Purchase #4	$71.93	12.290%	$80.7702	$80.77	$80.75	$80.80
Purchase #5	$174.88	6.135%	$185.6089	$185.61	$185.60	$185.60
Purchase #6	$196.30	5.335%	$206.7726	$206.77	$206.75	$206.80
Purchase #7	$112.36	9.804%	$123.3758	$123.38	$123.40	$123.40
7 purchase totals =	$1,080.56		$1,189.6974	$1,189.69	$1,189.65	$1,189.80