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	$92.95	10.194%	$102.4253	$102.43	$102.45	$102.40
Purchase #2	$120.34	9.622%	$131.9191	$131.92	$131.90	$131.90
Purchase #3	$92.26	8.124%	$99.7552	$99.76	$99.75	$99.80
Purchase #4	$151.60	8.614%	$164.6588	$164.66	$164.65	$164.70
Purchase #5	$108.35	4.411%	$113.1293	$113.13	$113.15	$113.10
Purchase #6	$237.74	11.196%	$264.3574	$264.36	$264.35	$264.40
Purchase #7	$121.64	12.324%	$136.6309	$136.63	$136.65	$136.60
7 purchase totals =	$924.88		$1,012.8760	$1,012.89	$1,012.90	$1,012.90