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	$111.72	13.721%	$127.0491	$127.05	$127.05	$127.00
Purchase #2	$156.30	6.413%	$166.3235	$166.32	$166.30	$166.30
Purchase #3	$201.90	11.317%	$224.749	$224.75	$224.75	$224.70
Purchase #4	$158.65	13.127%	$179.476	$179.48	$179.50	$179.50
Purchase #5	$144.83	8.341%	$156.9103	$156.91	$156.90	$156.90
Purchase #6	$107.69	10.797%	$119.3173	$119.32	$119.30	$119.30
Purchase #7	$75.81	7.106%	$81.1971	$81.20	$81.20	$81.20
7 purchase totals =	$956.90		$1,055.0223	$1,055.03	$1,055.00	$1,054.90