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	$225.62	3.789%	$234.1687	$234.17	$234.15	$234.20
Purchase #2	$193.70	9.225%	$211.5688	$211.57	$211.55	$211.60
Purchase #3	$215.90	13.258%	$244.524	$244.52	$244.50	$244.50
Purchase #4	$92.41	8.111%	$99.9054	$99.91	$99.90	$99.90
Purchase #5	$90.99	4.609%	$95.1837	$95.18	$95.20	$95.20
Purchase #6	$225.40	9.493%	$246.7972	$246.80	$246.80	$246.80
Purchase #7	$83.54	7.824%	$90.0762	$90.08	$90.10	$90.10
7 purchase totals =	$1,127.56		$1,222.2240	$1,222.23	$1,222.20	$1,222.30