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	$162.98	6.658%	$173.8312	$173.83	$173.85	$173.80
Purchase #2	$73.53	4.199%	$76.6175	$76.62	$76.60	$76.60
Purchase #3	$81.34	9.518%	$89.0819	$89.08	$89.10	$89.10
Purchase #4	$121.28	5.508%	$127.9601	$127.96	$127.95	$128.00
Purchase #5	$102.63	9.235%	$112.1079	$112.11	$112.10	$112.10
Purchase #6	$175.59	6.336%	$186.7154	$186.72	$186.70	$186.70
Purchase #7	$127.69	9.770%	$140.1653	$140.17	$140.15	$140.20
7 purchase totals =	$845.04		$906.4793	$906.49	$906.45	$906.50