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	$55.56	7.123%	$59.5175	$59.52	$59.50	$59.50
Purchase #2	$155.85	7.162%	$167.012	$167.01	$167.00	$167.00
Purchase #3	$112.46	8.197%	$121.6783	$121.68	$121.70	$121.70
Purchase #4	$138.28	3.536%	$143.1696	$143.17	$143.15	$143.20
Purchase #5	$115.83	6.352%	$123.1875	$123.19	$123.20	$123.20
Purchase #6	$115.70	3.730%	$120.0156	$120.02	$120.00	$120.00
Purchase #7	$96.91	4.827%	$101.5878	$101.59	$101.60	$101.60
7 purchase totals =	$790.59		$836.1683	$836.18	$836.15	$836.20