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	$86.34	11.397%	$96.1802	$96.18	$96.20	$96.20
Purchase #2	$105.58	6.291%	$112.222	$112.22	$112.20	$112.20
Purchase #3	$119.96	6.208%	$127.4071	$127.41	$127.40	$127.40
Purchase #4	$196.55	8.630%	$213.5123	$213.51	$213.50	$213.50
Purchase #5	$233.58	9.131%	$254.9082	$254.91	$254.90	$254.90
Purchase #6	$222.93	13.855%	$253.817	$253.82	$253.80	$253.80
Purchase #7	$53.30	7.265%	$57.1722	$57.17	$57.15	$57.20
7 purchase totals =	$1,018.24		$1,115.2190	$1,115.22	$1,115.15	$1,115.20