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	$119.44	6.467%	$127.1642	$127.16	$127.15	$127.20
Purchase #2	$159.70	13.696%	$181.5725	$181.57	$181.55	$181.60
Purchase #3	$35.81	3.536%	$37.0762	$37.08	$37.10	$37.10
Purchase #4	$26.32	10.401%	$29.0575	$29.06	$29.05	$29.10
Purchase #5	$22.80	3.216%	$23.5332	$23.53	$23.55	$23.50
Purchase #6	$86.41	4.474%	$90.276	$90.28	$90.30	$90.30
Purchase #7	$62.66	7.696%	$67.4823	$67.48	$67.50	$67.50
7 purchase totals =	$513.14		$556.1619	$556.16	$556.20	$556.30