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	$212.89	13.460%	$241.545	$241.55	$241.55	$241.50
Purchase #2	$143.91	5.370%	$151.638	$151.64	$151.65	$151.60
Purchase #3	$95.82	3.489%	$99.1632	$99.16	$99.15	$99.20
Purchase #4	$127.79	6.788%	$136.4644	$136.46	$136.45	$136.50
Purchase #5	$43.36	5.461%	$45.7279	$45.73	$45.75	$45.70
Purchase #6	$242.25	8.118%	$261.9159	$261.92	$261.90	$261.90
Purchase #7	$213.86	11.708%	$238.8987	$238.90	$238.90	$238.90
7 purchase totals =	$1,079.88		$1,175.3531	$1,175.36	$1,175.35	$1,175.30